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THE   DIURNAL  COURSE 
OF  EFFICIENCY 


BY 

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THE  SCIENCE  PRESS, 

Sub-Station  84,  New  York  City. 


THE  DIURNAL  COURSE 
OF  EFFICIENCY 


BY 

HOWARD  D.  MARSH,  Ph.D. 


ARCHIVES    OF 
PHILOSOPHY,    PSYCHOLOGY    AND    SCIENTIFIC   IVIETHODS 


EDITED    BT 

J.  McKEEX  CATTELL,  and  FBEDEBICK  J.  E.  WOODBBIDGE 


No.    7,  July,   1906 


Columbia  University  Contributions  to  Philosophy  and  Psychology,  Tol.  XIT,  No.  3. 


NEW   YORK 
THE   SCIENCE   PRESS 


'C 


Press  of 

The  new  era  printing  Company 

lancaster,  pa. 


TABLE    OF    CONTENTS 


PAGK 

Part  A.     Introduction 1 

Part  B.     Diurnal    Course    of    Psychophysiological    Effi- 
ciency      4 

I.    Vital  Activities   4 

1.  Secretion,  Urination,  Evaporation  4 

2.  Circulation,  Respiration,  Temperature   4 

3.  Deaths  relative  to  Time  of  Day 9 

4.  Brief  Summary  13 

II.    Sensory  Activities 13 

1.  Sight,  Color-sense,  Hearing 13 

2.  Skin-sensitivity,  Pressure-sense  14 

3.  Brief  Summary   14 

III.    Motor  Activities 14 

1.  Subhuman   Data    14 

(1)  Plant  Life   14 

(2)  Animal  Life 15 

2.  Human  Data 15 

(1)  General  Characteristics  of  Writer's  Methods  and 

Experiments  15 

(2)  Actual  Tests  and  Results— Writer's  and  Others'  17 

a.  Speed  and  Accuracy  of  Movement 17 

6.  Normal  Muscular  Power 24 

(a)   Small  and  Large  Muscular  Groups 24 

(&)   Comparative  Functioning  of  Such  Groups  31 

(c)  Bilateral  Symmetry 31 

c.  General  Motor  Control  32 

d.  Complex  Motor  Activity— Athletic  Perform- 

ances and  Manual  Labor 32 

3.  Brief  summary 40 

iii 


iv  CONIENTS 

PAGE 

Part  C.    Diurnal  Course  of  Mental  Efficiency 42 

I.    The  Simpler  Mental  Activities 42 

1.  Attention 42 

2.  Discrimination— Letters  and  Forms 44 

3.  Association— Reaction-time,   Naming   Colors,   Word 

Associations 46 

4.  Memory    (mechanical)- Visual,    Auditory,    Visual- 

auditory  50 

II.    The  More  Complex  Mental  Activities 53 

1.  Arithmetic— Addition,  Mental  and  Written  Multi- 

plication    53 

2.  Translating  French ;  Scoring  Death  Eecords 55 

3.  School  Examinations  and  School  Marks  57 

4.  Students'  and  Authors'  Preferred  Hours  for  Work  59 
III.    Brief  Summary 69 

Part  D.     Chief  Causal  Factors  in  the  Diurnal  Efficiency 

Curve 71 

I.     Night-day  Rhythm — Sleep  and  Activity 71 

II.     Habits,  Meals,  etc 74 

III.  Fatigue  and  Feelings  of  Fatigue 77 

1.  Muscular  Fatigue 78 

2.  Mental  Fatigue 78 

(1)  Measured  by  Motor  Inefficiency 78 

(2)  Measured  by  Sensory  Inefficiency 79 

(3)  Measured  by  Mental  Inefficiency 82 

IV.  Inertness  and  Nervousness 88 

V.    Sex  and  Age 90 

VI.    Brief  Summary 91 

Part  E.     Conclusion 93 

Bibliography 97 


THE  DIURNAL  COURSE  OF  EFFICIENCY 

•   A.    INTRODUCTION 

Recurrence  of  phenomena  is  the  source  of  all  scientific  knowl- 
edge. Rhythmic  recurrence  in  nature  is  well  known;  for  physics, 
it  is-  perhaps  the  most  general  and  fundamental  characteristic,  under- 
lying the  theories  of  the  mechanics  of  motion,  sound,  heat,  light  and 
electricity.  The  student  of  astronomy  finds  the  movements  of 
heavenly  bodies  marked  by  like  repetition.  It  appears  in  biology 
in  a  less  regular  way  in  the  growth  changes  of  vegetable  and  animal 
bodies  and  in  a  more  general  way  in  the  successive  generation  of 
species ;  while  evolution  as  a  whole  is  rather  completely  expressed  in 
alternation  of  integration  and  disintegration.  Social  life,  in  all  its 
historic  aspects,  gives  evidence  of  epochal  development,  and  some 
sociologists  have  gone  so  far  as  to  make  repetition  (as  imitation,  etc.) 
the  warp  of  the  whole  social  fabric.^  Nearer  the  point  of  the 
present  research  are  particular  seasonal  changes  in  individual  life 
— yearly,  quarterly,  monthly,  weekly,  daily — of  whose  existence  we 
have  hints  in  various  anthropological,  physiological  and  pathological 
data,  more  or  less  closely  connected  with  the  sexual,  religious  and 
emotional  life.- 

This  paper  deals  only  with  the  question  whether  there  are  nor- 
mally recurring  variations  of  ability  at  different  periods  of  the  day. 
The  discussion  of  this  question  is  not  to  be  found  in  general  works 
on  psj^chology,  however  modern,  but  in  sundry  monographs  and 
journal  articles  appearing  in  the  last  fifteen  years.  This  means  that 
the  more  conservative  psychologists  are  not  yet  ready  to  accept  such 
recurrence  as  a  fact.  But  the  investigators  themselves  seem  to 
consider  it  quite  confirmed,  despite  the  disagreements  of  their  results 
when  intercompared. 

Part  of  this  assurance  may  be  due  to  ignorance  of  what  others 
have  found.  The  good  side  of  this  is  that  experimentation  under 
such  conditions  has  less  tendency  to  bias,  to  which  workers  in  indi- 
vidual psychology  are  perhaps  more  exposed  than  are  those  in  other 
parts  of  the  experimental  field.      We  want  not  only  the  subjective 

^  For  complete  theory,  see  G.  Tarde's  Laics  of  Imitation  and  other  social 
writings. 

^Of  course  there  is  no  doubt  about  the  monthly  rhythm  in  females.  For 
other  suggested  ones,  see  H.  Ellis,  The  Psych,  of  Sex,  2.      1902. 


2  DIURNAL    COURSE    OF   EFFICIENCY 

satisfaction,  but  also  the  objective  recognition,  of  having  obtained 
results  with  a  definite  pointing— which  'show  something'.  But  that 
this  should  be  exhibited  from  the  negative  side  seems  often  as  objec- 
tionable to  the  searcher  as  discovery  of  no  'general  tendency'. 

The  writer  aims  to  present  all  the  important  work  hitherto  pub- 
lished, having  direct  bearing  on  the  problem.  On  account  of  the 
scope  of  the  latter,  no  collection  of  this  material  at  any  one  point 
is  attempted,  but  it  is  introduced  where  most  pertinent.  The 
greatest  lack  in  all  this  work  lies  in  two  things— inextensiveness  of 
the  experimental  series  and  omission  of  quantitative  expression  of 
the  reliability  of  the  results. 

It  is  easy  to  account  for  the  first  of  these  deficiencies  when  one 
remembers  the  nature  of  the  problem,  affecting  as  it  does  the  whole 
duration  of  the  day.  This  makes  it  hard  indeed  to  secure  persons  to 
act  as  subjects.  If  the  tests  are  short,  they  must  be  repeated  on  a 
great  number  of  days,  in  which  case  the  various  conditions  must  be 
so  much  the  longer  controlled;  if  they  are  individually  more  ex- 
tended and  adequate,  they  demand  most  of  the  subjects'  time  for  the 
days  on  which  they  are  taken,  and  in  this  case  accidental  disturb- 
ances are  more  costly.  Therefore  the  investigator  is  inclined  to 
reduce  either  the  number  of  days,  the  number  of  periods  per  day, 
the  number  of  trials  per  period  or  the  number  of  subjects  tested. 

This  being  true,  the  second  lack  mentioned  is  easily  explained. 
The  neglect  to  calculate  the  averages  obtained — a  very  serious  omis- 
sion when  differences  are  small  and  results  not  always  harmonious — 
arises  partly  from  the  feeling  that  the  material  at  hand  is  too  meager 
to  justify  the  calculus  of  probabilities.  An  additional  difficulty  is 
that  in  a  series  of  tests  day  after  day  the  curve  of  diurnal  variation 
is  complicated  with  the  curve  of  progressive  improvement  due  to 
practise.  This  makes  it  especially  hard  to  calculate  the  reliability 
of  the  averages  for  the  different  hours  of  the  day.  And  even  the 
mere  labor  of  the  tests  and  computations  is  a  deterrent ;  for  it  is 
clear  that  if  500  trials  are  thought  necessary  to  establish  a  reliable 
measure  of  any  function,  ten  times  that  many  and  ten  times  the  cal- 
culations will  be  required  to  establish  it  for  ten  periods  of  the  day. 
Other  minor  deterrents  might  be  enumerated  that  operate  in  certain 
cases. 

One  other  occasion  for  criticism  of  the  works  referred  to  is  found 
in  the  fact  that  the  tests  for  the  different  parts  of  the  day  have  not 
always  been  made  on  the  same  day.  Such  procedure  implies  the 
belief  that  the  absolute  ability  one  exhibits  on  one  day  is  the  same 
as  he  would  manifest  at  the  same  hour  the  next  day  or  any  subse- 
quent one :   it  takes  no  account  of  accidental  influences,   practise 


INTRODUCTION  3 

effects  and  other  inherent  factors  of  change.  To  keep  clear  of  these 
errors,  the  tests  for  the  different  hours  of  the  day  should  be  made 
on  the  same  days. 

My  own  work  is  not  free  from  the  first  of  these  criticisms,  but 
avoids  the  remaining  two. 

In  addition  to  presenting  the  work  of  others,  the  author,  by  a 
great  variety  of  extended  tests  upon  himself,  has  been  able  to  estab- 
lish definitely  the  course  of  diurnal  changes  for  one  normal  subject. 
Six  male  graduate  students,  one  female  graduate,  and  a  group  of 
sixteen  female  undergraduates  were  likewise  employed  for  both 
motor  and  mental  tests,  and  the  measurement  of  the  hourly  product 
of  22  female  factory  operatives  contributed  additional  data.  The 
tabulation  of  human  deaths  for  time  of  day;  the  results  of  school 
examinations  and  recitation  marks  for  different  diurnal  periods; 
the  best  times  of  day  for  athletic  performance  and  for  intellectual 
composition ;  in  short,  as  wide  a  class  of  pertinent  matter  as  could 
be  secured  has  been  applied  to  the  solution  of  the  question  of  diurnal 
changes  of  efficiency. 

In  the  experimental  portion  of  the  present  work,  much  use  has 
been  made  of  tests  variously  employed  by  others.  The  aim  has  been 
to  get  such  variety  as  the  practical  limitations  of  application  would 
allow.  It  is  not  thought  that  together  they  give  a  measure  of  'gen- 
eral intelligence'  or  'general  motor  power'.  These  themselves  have 
rather  a  precarious  existence  since  analytical  psychology  has  taken 
an  experimental  turn.  Our  activities  are  recognized  as  much  more 
complex  than  they  seem,  and  tests  of  them,  on  the  basis  of  simplicity, 
may  not  be  productive  of  the  most  valuable  knowledge.  Especially 
is  this  true  of  adults,  to  whom  my  own  tests  were  chiefly  confined. 
Still  it  is  true  that  legitimate  and  interesting  results  have  been 
reached  in  the  past  and  that  accruing  experience  must  make  future 
eft'orts  more  fruitful.  As  the  total  outcome  of  his  research,  the 
author  is  not  prepared  to  'say  the  last  word'  about  diurnal  rhythms, 
but  hopes  that  something  worth  while  has  been  attained. 

Acknowledgments  are  due  to  Professor  Cattell  for  the  original 
proposal  of  the  problem  and  for  other  suggestions;  to  Professors 
Thorndike,  Woodwcrth  and  JMejdan,  of  Columbia  University,  for 
assistance  of  various  kinds;  to  those  who  acted  as  subjects  at  much 
personal  inconvenience ;  to  certain  officers  and  employees  of  the 
manufacturing  firms  of  Dennison  and  Sons,  J.  English  and  Sons 
and  the  Trow  Directory  Company,  of  New  York  City,  for  courtesies 
extended  during  observational  work  in  their  respective  factories ; 
to  Dr.  Guilfoy,  registrar  of  the  City  Health  Department;  and  to 
other  individuals  who  contributed  in  different  ways. 


B.     THE    COURSE    OF   PSYCHOPHYSIOLOGICAL 
EFFICIENCY 

I.    Vital  Activities 

Any  strict  line  of  demarcation  between  so-called  physical  and 
mental  life  does  not  exist  in  reality  and  is  maintained  primarily  for 
convenience  in  dealing  with  the  complex  phenomena  of  life.  For 
the  data  to  be  presented  in  this  section  the  term  psychophysiological 
seems  best,  since  from  the  physical  side  only  the  functional  aspect 
is  dealt  with.  What  will  be  called  'vital'  activities  are  on  the  mental 
side  directly  concerned  with  emotion;  'sensory',  with  cognition;  and 
'motor,'  with  volition,  as  the  words  are  commonly  accepted.  The 
idea  is  not  to  support  a  three-faculty  psychology  nor  to  stand  sponsor 
for  a  rigid  meaning  of  the  terms  employed.  But  a  more  systematic 
presentation  of  the  subject  can  be  given  by  adherence  to  the  order 
named. 

Considering  the  length  of  time  that  medicine  has  been  studied, 
or  even  that  physiology  has  been  a  separate  science,  one  would  ex- 
pect to  find  the  matter  of  physiological  rhythms  fully  discussed. 
However,  the  text-books  here  are  as  barren  as  those  in  psychology 
with  respect  to  the  general  problem.  The  first  and  only  systematic 
collection  of  results  was  published  by  Vierordt  in  1888\  The  actual 
work  was  done  by  various  medical  men  between  1840  and  1880,  and 
much  of  it  must  be  considered  unreliable,  particularly  where  the 
conditions  of  experimentation  or  observation  are  not  stated.  Only 
such  figures  as  seem  most  trustworthy  will  be  quoted. 

1.    Secretion,  Urination,  Evaporation 

Vierordt 's  results  here  have  no  value  in  themselves  without  fuller 
information  as  to  number  of  subjects  and  their  habits  of  life,  their 
age,  sex,  health,  etc.,  together  with  the  length  and  method  of  experi- 
mentation.     The  following  are  less  deficient  in  these  respects. 

2.    Circulation,  Respiration,  Temperature 

1.  Circulation. — The  most  commonly  accepted  view  with  regard 
to  pulse  rate  is  that  the  maximum  occurs  in  early  morning,  followed 
by  a  steady  decline  till  after  midnight,  broken  only  by  the  temporary 

"■  Daten  und  Tahellen.      1888. 


COURSE    OF   PSYCHOPHYSIOLOGICAL    EFFICIENCY  5 

influence  of  meals  and  accidental  excitements.  This  seems  only 
partly  true.  The  correctness  of  the  first  statement  is  greater  the 
nearer  to  arising  the  record  is  taken,  as  will  be  indicated  below. 
The  following  table  gives  most  of  what  material  could  be  gathered 
on  this  matter,  together  with  some  of  my  own. 

Table  I.      Pulse  Rate  and  Time  of  Day. 


7  A.M. 

8     9  10  11    12  1  P.M.  2  3  4 

5 

6  7 

8 

9  10 

11  12 

1 

*  74  71  70   69  81   84  82  77 

76 

75  75 

2, 

68  *            71       68 

68 

*72 

2: 

73  *            83       76 

68 

*69 

2, 

90  *           105       97 

82 

*97 

3 

68 

*  81   87  73  79   67  82   83  73  73 

70 

*85 

4, 

56  *            72 

69 

* 

65 

4, 

72 

*  86   83  81  76   73  79   77  75  72 

78 

*84  82 

77 

73  70 

69  68 

4, 

71 

*   78   74   70      77   72 

70 

72  * 

78 

76   71 

4, 

84 

*  94   98  ■  84   78  77  -  82   76 

*86 

72 

1 — Yierordt.      Self,  number  of  days  not  stated. 

2 — Binet.      2i  self,  7  days;  2.  male  adult,  2  days;  23  female  adult,  2  days. 
3 — Storey.     Self,  average  of  0  to  10  determinations. 

4 — Marsh.      4i  male  adult,  0  days;   4.  male  adult,  15  days    (summer);   43 
same,  12  days   (winter)  ;  4^  female  adult,  7  days. 
* — Indicates  occurrence  of  meals. 

Not  all  the  series  approach  completeness.  Small  dependence 
can  be  placed  on  1^ ;  Binet"  says  of  his  own  that  ' '  they  are  three 
single  curves  chosen  from  a  great  number  because  of  the  distinctness 
of  the  tracings",  not  saying  that  they  are  even  representative  ones; 
4i  is  a  short  series  but  with  small  probable  error. 

The  first  four  and  4^  show  the  maximum  rate  at  about  1-2  p.m. 
(2  also  at  9  p.m.),  the  othei-s  at  8-9  a.m.  The  changes  to  which  we 
are  subjected  on  awakening  act  as  excitants  and  largely  cause  the 
apparently  high  early  morning  rate.  Change  of  position  alone  has 
great  influence.  Ten  mornings,  in  my  own  case,  the  rate  two  minutes 
after  arising  averaged  81,  as  compared  with  72  twenty  minutes  later ; 
and  again  in  the  second  series  the  figures  were  respectively  81  and 
71.  Subject  4^  did  the  same  thing  a  like  number  of  days,  taking  an 
additional  record  in  bed  several  minutes  before  arising.  Her  aver- 
ages were  79,  87  and  84.  These  facts  suggest  what  small  reliance 
can  be  placed  on  bare  pulse  figures  in  tables.  AYhat  seems  to  be 
true  here,  aside  from  the  doubly  induced  increase  due  to  rising  and 
eating,  is  first  a  morning  rate  less  high  and  less  well  sustained  than 
the  afternoon  rate ;  second,  a  higher  female  than  male  rate,  with 

^Yet,  as  late  as  1900,  the  Am.  Text-book  of  Physiol,  quotes  these  figures  as 
bases  for  conclusions.      This  shows  how  meager  is  the  information. 

" '  Le  Changements  de  Forme  du  Pouls  Capillaire,'  L'Annee  Psych.,  3.     1897. 


6  DIURNAL    COURSE    OF   EFFICIENCY 

tendency  to  an  earlier  maximum^ ;  and  third,  a  general  rate  higher 
than  the  70  so  long  accepted  as  about  the  average. 

As  to  the  first  point,  the  order  is  sustained  by  a  recent  study  of 
blood  and  pulse  pressures  made  by  Erlanger  and  Hooker^  with  one 
adult  subject.  Five  extensive  tables  show  the  results  obtained  for 
five  days,  at  different  hours  from  8  a.m.  till  10:30  p.m.,  but  their 
reproduction  here  is  forbidden  by  their  great  length  and  uncertain 
value.  However,  the  authors  draw  this  conclusion:  "We  therefore 
can  distinguish  a  gradual  increase  of  pulse-pressure  [directly  pro- 
portional to  pulse-rate  according  to  them — p.  294]  throughout  the 
day  upon  which  is  built  up  the  wave-like  increase  that  follows  upon 
the  ingestion  of  meals"  (p.  343).  "There  seems  to  be  no  relation 
between  the  amount  of  food  ingested  and  the  height  and  duration 
of  the  post-prandial  [fundamental]  rise"  (p.  344). 

In  addition  to  this  direct  evidence  there  are  other  facts  in  favor 
of  the  view  that  the  pulse  is  normally  lower  in  the  morning  than 
later  in  the  day.  IMuscular  and  brain  activity  heighten  the  pulse 
rate  on  account  of  the  increase  in  waste  products  sent  to  the  heart. 
If  it  be  true  that  a  greater  muscular  power  accompanies  increased 
rate  of  circulation,  as  shown  by  Zablondousky^  and  Maggiora^  with 
massaged  muscles,  and  by  Kronecker^  with  injection  of  blood  into 
fatigued  muscle,  then,  according  to  the  traditional  pulse  theory,  the 
greatest  strength  might  be  expected  in  the  early  morning.  As  a 
matter  of  fact,  it  is  probably  least  then,  as  will  be  shown  later. 

Periodicity  in  pulse  intensity  and  blood  pressure,  dicrotism  and 
the  rapidity  of  vascular  reflex  have  been  investigated,  but  the  results 
are  unimportant. 

2.  Respiration. — One  expects  to  find  a  positive  correlation  be- 
tw^een  pulse  rate  and  respiration  and  temperature,  as  they  have  a 
common  dependence  on  the  amount  of  metabolism  in  the  body,  the 
latter  in  turn  being  largely  proportional  to  the  excitement  or  activity 
at  any  period.     And  it  is  found  to  be  so  in  fact. 

Vierordt's  maximum  for  himself  was  at  2  p.m.  for  rapidity  of 
respiration  and  volume  of  air  and  of  COo  expired,  and  minimum  at 

^  The  high  night  rate  of  23  is  due  to  the  evening  meal  and  no  comparable 
morning  figure  is  shown,  while  the  case  of  44  shows  a  considerable  falling  off 
towards  night.  Guy  and  Knox,  per  Vierordt,  found  a  higher  rate  for  children 
Avith  an  early  morning  maximum.  Miss  N.  Norsworthy,  of  Teachers  College, 
in  a  recent  research,  the  results  of  which  are  as  yet  unpublished,  found  for 
girls  under  15  years  a  rate  of  9.5.5,  and  above  15,  of  93 — 295  cases;  for  boys 
under  13,  95,  and  above  13,  85 — 253  cases. 

2 '  An  Experimental  Study  of  Blood-pressure  and  Pulse-pressure  in  jNIan,' 
Johns  Hopkins  Hosp.  Reps.,  12:  145-378.     1904. 

^  J.  Joteyko,  '  Revue  Generale  sur  la  Fatigue  IMusculaire,'  L'Annee  Psych., 
5.     1898. 


COUBSE    OF    P.^YCHOPHYSIOLOGICAL    EFFICIENCY  7 

7  P.M. — the  last  hour  of  his  series.  Binet's  maximum  occurred  at 
7-9  P.M.  and  minimum  at  8  a.m.,  his  series  being  from  8  a.m.  to 
8:40  p.m.  Tigerstedt^  (after  Jiirgensen — see  Fig.  1)  finds  the 
maximum  volume  of  COo  at  5-8  p.m.  and  minimum  at  4-8  a.m. 


Fig.    1.     Normal  .Variations  in  Body  Temperature    (after  Tigerstedt). 

Johannson^  tinds  that  the  greatest  quantity  of  CO2  is  given  off 
by  an  active  subject  from  8-12  a.m.  and  the  least  from  4-6  a.m.; 
this  was  practically  true  also  during  perfect  rest.  His  experiments 
were  on  himself,  in  six-hour  courses  of  activity  and,  again,  of  in- 
activity (in  bed),  requiring  different  days  to  cover  the  whole  twenty- 
four  hours. 

In  accord  with  this  evidence  are  certain  data  obtained  from 
spirometric  tests  of  Filipinos  at  the  St.  Louis  Exposition,^  where 
72  Avere  tested  for  lung  capacity  in  the  morning  and  41  in  the  after- 
noon. The  average  for  the  morning  was  170.0  cu.  in.,  with  a  prob- 
able error  of  1.76 ;  and  for  the  afternoon,  177.2,  with  P.E.  2.60.  In 
my  own  case,  eight  trials  at  each  period  showed  averages  as  follows : 
7-8  a.m.,  189;  9-10  a.m.,  192;  11-12  a.m.,  191;  1-2  p.m.,  188;  3- 
4  P.M.,  192;  5-6  p.m.,  192;  7-8  p.m.,  193;  9-10  p.m.,  191.  This  fol- 
lows closely  the  curve  of  my  motor  ability  as  found  by  many  tests. 

3.  Temperature. — Reference  to  Table  II.  and  Fig.  1  makes  it 
evident  that  the  temperature  reaches  the  highest  point  about  5- 
8  P.M.  and  the  lowest  about  7  a.m.  Johannson  finds  the  same  true 
for  diurnal  activity  or  rest  conditions.  Attention  is  called  to  the 
close  similarity  of  the  curves  in  Fig.  1,  and  to  the  close  agreement 
of  the  results  cited. 


^  Lehrbiich  der  Physiologie.      1902. 

^ '  Ueber  die  Tagesschwankungen  des  Stoffwechsels  imd  der  Korpertemper- 
atur,  Skand.  Archiv.  fur  Physiol.,  8.      1898. 

^  Fuller  reference  to  this  work  will  be  made  later. 


DIURNAL    COURSE    OF   EFFICIENCY 
Table  II.      Body  Tkmpekature  and  Time  of  Day. 


6  A.M. 

7 

8 

9 

10 

11 

12       1  P.M. 

2 

3 

4 

5 

1, 

37.9  * 

*38.4 

38.2 

h' 

37.5  * 

*37.9 

37.8 

2, 

36.4 

36.7  * 

37.0 

37.2 

37.1 

*37.3 

37.5 

2, 

36.6 

36.8  * 

37.1 

37.1 

37.1 

*37.2 

37.3 

3, 

33.3 

32.8 

32.9 

32.5 

*  32.5 

33.6 

34.2  *  35.5 

34.5 

33.5 

33.9 

33.2 

3, 

36.4 

36.9 

37.2 

37.2 

*37.3 

37.4 

37.4  *  37.5 

37.4 

37.4 

37.4 

37.4 

6  P.M. 

7 

8 

9 

10 

11 

12 

1A.M. 

2 

3 

4 

5 

1, 

38.4 

*38.5 

1, 

38.0 

*  38.2 

2i 

37.4 

*37.2 

36.9 

2I 

37.1 

*37.1 

36.7 

3, 

34.2 

35.6 

36.0 

35.9 

35.8 

35.7 

35.7 

35.5 

35.2 

34.7 

35.0 

35.0 

3^ 

37.5 

37.5 

37.4 

37.2 

37.0 

37.0 

36.8 

36.8 

36.7 

36.6 

36.6 

36.4 

1 — Binet.      Ii  hand;   L  rectum;  self,  number  of  days  not  stated. 

2 — Vierordt.  2i  average  of  Jiirgensen,  Liebermeister,  Barensprung — 
rectum — days  not  stated ;  2;  average  of  Gierse,  Kallmann,  Liclitenfels,  Friihlich — 
mouth — days  not  stated. 

3 — Roemer.      3^  hand;   3.  rectum;   subjects  and  days  not  stated. 

* — Indicates  the  occurrence  of  meals. 

Some  very  interesting  experiments  by  Galbraith  and  Simpson^ 
on  the  temperature  wave  in  the  monkey  may  be  briefly  described 
here.  The  axillary  temperature  of  six  subjects  was  taken  every 
two  hours,  day  and  night,  under  different  conditions,  as  follows: 

(a)  Twelve  days— ordinary  conditions— fed  at  9  a.m.  and  at 
6  P.M. — period  of  activity,  9  a.m.  to  9  p.m.  ;  of  rest,  9  p.m.  to  9  a.m. 
Result:  rise  during  activity,  maximum  at  5  p.m.;  fall  during  rest, 
minimum  at  6  a.m.     This  occurred  every  day. 

(&)  Six  days— conditions  exactly  reversed  (artificial  light  at 
night)  — fed  at  6  a.m.  and  at  9  p.m.  Result:  complete  reversal  of  the 
diurnal  wave  in  24  hours;  maximum  at  2  a.m.  and  minimum  at 

5  P.M. 

(c)  Six  days— active  from  3  p.m.  to  3  a.m.,  etc.  Result:  similar, 
though  slower,  modification  of  the  wave ;  maximum  at  9  p.m.,  mini- 
mum at  noon. 

(d)  Six  days— in  darkness  during  entire  time,  etc.  Result:  wave 
became  irregular,  then  gradually  disappeared. 

(c)  Six  days— in  light  whole  time,  etc.  Result:  no  wave  shown, 
but  an  irregular  curve;  animals  irritable. 

To  verify  these  results,  experiments  on  birds  were  next  under- 
taken.-     The  owl  reached  the  maximum  at  night  and  the  minimum 

^ '  Conditions  Influencing  the  Diurnal  Wave  in  Temperature  of  Monkey,' 
Jour,  of  Physiol.,  30,  2:  20;  Proc.  Physiol.  80c.      1903. 

^ '  Temperature  Variations  in  Nocturnal  and  Other  Birds,'  op.  cit. 


COURSE    OF   PSYCHOPHYSIOLOGICAL   EFFICIENCY 


9 


in  daytime.  The  thrush,  on  the  other  hand,  reached  these  points  at 
noon  and  midnight,  the  difference  amounting  to  over  5  degrees  centi- 
grade. Gulls,  pigeons  and  three  varieties  of  ducks  showed  similar 
variations ;  the  smaller  the  bird  the  greater  was  the  diurnal  variation. 
The  recurrent  rhythm  of  day  and  night  and  the  consequent 
habitual  alternation  of  activity  and  rest  are  seen  to  be  the  all- 
important  factors  here,  as  they  are  also,  probably,  for  men.  Unfor- 
tunately, no  analogous  human  experiments  have  yet  been  made, 

3,    Deaths  Relative  to  Time  of  Day 

Kirkpatrick,^  discussing  fatigue,  makes  the  remark  (p.  327)  that 
since  more  deatlis  occur  about  4  a.m.  than  any  other  hour,  vitality 
is  then  probably  lowest.  He  cites  no  authority  for  this  statement, 
nor  has  the  writer  been  able  to  locate  any  in  print,  though  it  appears 
to  be  widely  accepted  as  a  fact,  even  by  physicians  who  have  been 
personally  questioned.      To  determine  the  facts  36,000  records  of 

Table  III.     Deaths  Relative  to  Time  of  Day. 


Description  of 
Group. 

Zymotic  cases 

All  causes 

Males 

Females 

Age— M.  &  F, 

1-  5 

6-25 

26-45 

46-65 

66-95 

Season,  M.  &  F. 

Nov. -Feb 

Mar.-June 

July-Oct 

Description  of 
Group. 

Zymotic  cases.... 
All  causes 

Males 

Females 

Age— M.  &  F. 

1-  5 

6-25 

26-45 

46-65 

66-95 

Season,  M.  &  F. 

Nov.-Feb 

Mar.-June 

Julv-Oct 


Total 
No. 

15,616 
23,439 
11,991 
11.448 


6  A.M.    7 


10 


11 


12    1P.M.    2 


660  659  579  631  628  668  665  598  695  687  697  693 

10031007  953  959  970  981  782  955  980100910061054 

493  525  491  506  501  501  409  484  471  505  500  562 

510  482  462  453  469  480  373  471  509  504  501  492 

227  211  209  171  178  195  152  176  202  203  180  203 

113  137  115  130  122  125  96  117  123  105  122  119 

268  272  245  261  272  264  229  268  275  296  286  273 

241  229  237  248  238  242  185  239  239  253  247  276 

154  158  147  149  160  155  120  155  141  152  166  183 

369  359  348  360  380  330  270  324  312  371  372  361 

358  381  373  339  325  372  269  336  375  357  351  378 

276  267  232  260  265  279  243  295  293  281  278  315 


Total 
No. 


6  P.M. 


10 


11 


12  1A.M. 


709  623  603  634  688  723  412  669  624  651  660  663 

994  948  984  947  9421107  8471026  994  981  9861029 

530  493  520  492  471  540  441  514  490  532  485  535 

464  455  464  455  471  567  406  512  504  449  501  494 

201  181  181  200  162  219  138  200  211  190  190  212 

119  94  135  127  127  135  98  122  130  107  114  130 

256  275  267  263  263  281  248  285  250  301  268  282 

272  245  249  208  238  300  201  286  258  245  244  253 

146  153  152  149  152  172  162  133  145  137  172  152 

325  324  375  336  327  434  323  410  379  348  361  383 

354  351  319  333  331  377  276  318  332  332  359  369 

315  273  290  278  284  296  248  298  283  301  266  277 


^Fundamentals  of  Child  Study.      1903. 


10 


DIURNAL    COURSE    OF   EFFICIENCY 


deaths  occurring  in  New  York  City  in  1901  were  worked  over  by  the 
writer.  Those  cases  were  excluded  in  which  death  was  caused  by 
suicide  or  accident,  those  of  children  under  one  year  in  age,  and 
those  where  the  hour  was  omitted  from  the  doctor's  certificate. 
Males  and  females  were  recorded  separately  and  in  the  following 
age  groups:  1-5,  6-25,  26^5,  46-65,  66-95.  Three  seasons  of  the 
year  were  also  noted:  November-February  inclusive,  March-June, 
July-October.  For  each  of  the  months  3,000  cases  were  used,  but 
after  making  the  above  exclusions  only  23,439  remained.  In  addi- 
tion to  these.  Table  III.  reports  15,516  deaths  from  zymotic  diseases, 
which  had  been  tabulated  for  each  hour  of  the  day  in  the  official 
records  of  the  city  Health  Department  for  the  years  1876-79.  No 
others  were  found  for  subsequent  years,  up  to  date.  In  all  but  the 
first  group  6  a.m.  means  from  5  :30  to  6  :30 ;  what  it  means  in  the 
first  group  was  not  discovered. 


A.M    Noon 


PM.  M/D-NIDHT  AM. 


iPDcir-,    1    R    a   ip    /r  /2    I     ?    •J    i    y~fi    7    ?    ?   'P  <^-^   !    'F'I r ^—^'^oa 


400 
GOO 


400 

600 


Fig.  2. 


^>''  Females  -Broken L/ne 

Figures  at  the  sides  indicate  number  of  cases. 
Deaths  Relative  to  Time  of  Day — see  Table  III. 


This  table  and  these  curves  of  the  chief  groups  are  by  no  means 
easy  of  interpretation  as  they  stand.  This  is  mainly  due  to  one 
peculiarity,  affecting  every  group,  which  must  first  of  all  be  ac- 
counted for  if  possible.  This  is  the  notably  apparent  decrease  in 
deaths  at  the  noon  and  midnight  periods.  Its  occurrence  at  these 
particular  points  is  'prima  facie  evidence  that  a  real  fact  is  not  dis- 
closed, and  its  occurrence  in  all  groups  is  convincing  proof  of  some 
external  cause.  It  can  probably  be  explained  if  Kant's  philosophic 
theorizing  be  allowed — that  'man  is  by  nature  lazy'.      This  seems  a 


COURSE    OF   PSYCHOPHYSIOLOGICAL    EFFICIENCY  H 

far  cry  to  the  present  matter,  but  a  few  words  will  make  it  plain. 
The  attending  physician  must  certify,  as  to  the  hour  of  a  patient's 
death,  that  so-and-so  died  'at  —  m.'  This  works  happily  enough  till 
the  periods  in  question  are  involved,  when  immediately  arises  the 
necessity  of  writing  out  in  full  the  words  'noon'  and  'midnight'  for 
the  sake  of  their  clear  distinction.^  Rather  than  take  this  trouble, 
the  indifferent  doctor  will  do  one  of  two  things — either  leave  the 
space  blank  or  make  the  record  for  the  closely  preceding  or  suc- 
ceeding hours.  In  the  first  event  a  like  loss  is  occasioned  in  the  two 
periods,  since  the  record  does  not  then  differ  from  those  left  blank 
for  other  reasons,  all  of  which  records  had  to  be  excluded.  The 
cases  thus  affected  would  account  for  only  a  small  part  of  the  ap- 
parent decrease — possibly  one  tenth.  In  the  other  event,  the  ad- 
jacent periods  should  show  decided  increase.  That  is  precisely  what 
they  do  at  midnight,  sufficiently  to  smooth  the  curves  from  10  p.m. 
till  2  A.M.  inclusive,  as  indicated  by  the  dotted  lines  in  Fig.  2.  It  is 
not  so  evident  at  noon,  and  there  may  be  a  real  decrease  at  that  hour 
— a  possibility  somewhat  emphasized  by  the  1  o'clock  drop  in  the 
first  group. 

The  first  two  curves  are  similar  throughout,  save  at  noon.  "When 
corrected  as  suggested  they  are  easier  to  compare.  The  highest  rate 
in  each  occurs,  not  at  4  a.m.,  but  from  2  to  6  p.m.  ;  and  the  minimum, 
less  well  marked,  immediately  after— from  7  to  12  p.m.  An  exam- 
ination of  the  figures  of  the  sex  group  shows  much  the  same  order, 
the  females  reaching  a  slightly  earlier  maximum  than  the  males, 
while  3  A.M.  and  5  p.m.  are  the  only  points  of  notable  opposition. 
The  female  rate  is  more  regular  than  the  male.  In  the  age  group, 
26-45  most  resembles  the  female  curve  and  46-65  the  male.  In  the 
season  group,  the  July-October  curve  most  nearly  follows  that  for 
all  deaths. 

Just  what  these  results  mean  is  puzzling.  The  differences  are 
frequently  much  above  those  easily  accounted  for  by  chance.  While 
the  number  of  cases  seems  large,  it  is  only  about  one  fourth  large 
enough.      The  sub-groups  for  age  and  times  of  year  are  far  from 

^  This  would  not  be  the  case  if  many  people,  including  doctors,  did  not 
think  that  M  stands  for  midnight  as  well  as  for  meridian,  while  some  think 
it  stands  for  nothing  else.  The  first  set  of  figures  is  seen,  relative  to  the 
second,  to  show  a  much  less  noon  and  a  much  greater  midnight  drop.  This 
is  best  accounted  for  by  supposing  that  the  compiler  included  at  the  former 
period  all  cases  marked  '  12  M.,'  whereas  part  doubtless  belonged  to  the  latter 
period.  The  same  is  less  true  of  the  second  set  because  some  of  these  cases 
were  distributed  to  the  later  period.  Attention  is  called  to  the  fact  that  these 
points  are  disregarded  in  the  '  smoothings '  shown  in  Fig.  2,  but  should  be 
remembered  in  connection  with  the  further  discussion  of  the  curves. 


12  DIURNAL    COURSE    OF   EFFICIENCY 

being  extensive  enough  to  throw  adequate  light  on  the  causal  factors 
involved.  Even  after  combining  the  male  and  female  figures,  each 
period  of  these  groups  is  poorly  represented ;  but  such  a  combination 
is  scarcely  allowable.  Confining  attention  to  the  first  three  groups, 
the  venture  of  a  definite  opinion  might  be  hazarded. 

At  first  thought  one  would  be  tempted  to  infer  from  the  occurrence 
of  the  maximum  at  the  warmest  part  of  the  day,  that  the  heat  was 
the  important  factor.  But  inspection  of  the  seasonal  figures  shows  a 
much  lower  death  rate  in  July-October  than  in  winter,  while  the 
curve  for  the  summer  months  closely  resembles  the  general  curve. 
Heat  alone  offers  no  solution. 

The  following  theory  is  more  in  harmony  with  the  facts :  the 
vast  majority  of  these  people  died  of  disease  and  not  of  old  age. 
The  proportion  of  sudden  to  gradual  deaths  was,  on  the  whole,  small. 
The  'average  patient'  (to  generalize  for  adults)  on  awakening  is 
fed,  and  for  an  hour  his  death  rate  is  lowered,  food  influence  being 
often  eked  out  by  a  nap.  His  waking  troubles  begin  thereafter  and 
cause  a  rise  in  the  rate  till  at  noon  he  is  again  fed  and  reduced  to  a 
minimum  of  activity  for  an  hour  or  two.  Then  the  troubles  and 
frettings  are  resumed  more  vigorously,  the  body  having  now  become 
thoroughly  'warmed  up',  and  the  actions  responsive  to  this  increased 
state  of  stimulation  sap  the  energy  more  rapidly,  till  the  final  sur- 
render takes  place  about  5  or  6  p.m.  For  the  survivors,  there  is  at 
this  time  another  meal  and  consequent  lowering  of  the  curve,  which 
is  again  emphasized  by  longer  sleep,  during  which  there  is  a  gradual, 
slight  rise  in  rate  till  the  morning  awakening. 

This  idea  is  supported  by  the  time  of  occurrence  of  the  highest  and 
lowest  rates  in  the  age  groups.  A  close  scrutiny,  with  the  suggested 
smoothing  always  in  mind,  reveals  that  the  maximum  for  ages  1-5 
is  very  early  in  the  morning — before  9 ;  that  for  6-25,  from  7  to 
11  A.M. ;  that  for  26-45,  about  3  to  4  p.m.  ;  and  for  the  following 
years,  about  5  to  6  p.m.  The  curve  of  diurnal  activity  probably 
varies  rather  similarly  with  age.  A  large  increase  in  the  number  of 
cases  would  be  of  marked  value,  as  it  is  evident  that  these  groups 
are  not  only  too  wide,  but  are  also  rendered  too  heterogeneous  by  the 
sex  element.  The  minimum  locations  are  likewise  confirmatory,  as 
they  uniformly  occur  at  the  customary  points  of  least  activity — 
meal-times  and  night. 

At  all  events,  the  4  a.m.  idea  is  effectively  exploded.  The  cases 
are  numerous  enough  to  establish  this  point  reliably.  The  females 
of  the  second  group  show  a  drop  at  3  a.m.,  which  is  offset  by  a  male 
rise  and  hence  a  straight  line  appears  in  the  curve  of  the  whole 
group  for  this  part  of  the  night.     As  a  matter  of  fact,  the  time  from 


COURSE    OF   PSYCHOPHYSIOLOGICAL    EFFICIENCY  13 

1  to  5  A.M.  is  but  a  trifle  higher  in  death  rate  than  the  median  for 
the  whole  day.  The  body  temperature  and  expiration  of  COo,  as 
shown  by  Fig.  1,  would  lead  one  offhand  to  expect  the  greatest  num- 
ber of  deaths  about  4  or  5  a.m.  The  fact  that  they  do  not  come  at 
this  point  of  apparently  lowest  vitality,  throws  us  back  to  the  con- 
clusion already  drawn.  It  appears  paradoxical  to  call  the  point  of 
greatest  strength — a  fact  to  be  later  demonstrated — the  most  likely 
death  point,  yet  it  is  really  not  unreasonable.  It  is  well  known  that 
patients  usually  grow  worse  towards  evening.  The  successive  mo- 
ments of  pain  or  chafing  throughout  the  day  act  in  a  cumulative 
way  physiopsychologically,  causing  increased  irritation,  which  ex- 
cites to  the  expenditure  of  more  energy  than  the  system  can  afford 
to  lose. 

4.    Brief  Summary 

It  may  be  said  that,  in  a  general  way  and  ignoring  the  immediate 
effects  of  meals  as  far  as  possible,  the  heart  and  lung  functions  and 
body  temperature  tend  to  vary  alike,  beginning  with  a  very  early 
minimum — about  5  a.m.— and  increasing  to  a  late  afternoon  maxi- 
mum—  about  5  P.M.  There  is  ground  for  believing  that  women  reach 
an  earlier  maximum  than  men,  at  a  higher  rate,  and  children  a  still 
earlier  maximum  at  a  still  higher  rate.  Similar  facts  seem  to  hold 
good  in  the  case  of  animals,  where  it  is  found  that  the  periods  of 
rest  and  activity  determine  the  curve  entirely.  While  the  same 
maximal  period  holds  for  human  deaths,  the  minimal  one  is  from 
7  to  11  P.M.,  females  again  coming  to  an  earlier  maximum  than  males, 
and  young  children  to  a  very  early  one.  Contrary  to  what  one 
would  anticipate,  the  maximal  death  rate  in  each  of  these  groups 
fails  very  near  to  the  time  where  we  are  led  in  normal  life  to  look 
for  the  greatest  physical  efficiency,  as  evidenced  by  muscular  power. 
This  is  most  likely  due  to  the  fact  that,  in  the  main,  at  these  periods 
the  most  effective  stimuli  are  in  operation,  externally  and  internally, 
and  cause  an  over-expenditure  of  energy  from  which  it  is  impossible 
for  many  patients  to  ralty.  While  a  sort  of  physical  weakness  prob- 
ably exists  very  early  in  the  morning,  it  is  not  true,  as  held  by  pop- 
ular opinion,  that  we  are  'nearest  death'  at  that  particular  portion 
of  the  day. 

II.    Sensory  Activities 
1.    Sight,  Color-sense  and  Hearing 

In  some  psychological   experiments   on  various  peoples  at   the 
St.  Louis  World's  Fair,  in  which  the  author  assisted  those  in  charge 
of  this  section  of  the  exposition— Dr.  R.  S.  Woodworth  and  Mr.  F. 
2 


14  DIURNAL    COURSE    OF   EFFICIENCY 

G.  Bruner,  of  Columbia  University— the  sight  and  hearing  of  over 
100  Filipinos  were  tested  between  9  :30  a.m.  and  12  m.,  or  between 
2  P.M.  and  4:30  p.m.  For  acuity  of  vision  the  so-called  E-test  was 
used,  in  which  lines  of  E  's  of  successively  smaller  sizes  and  pointing 
in  different  directions  are  arranged  on  a  chart  like  the  ordinary 
letter  charts  for  optical  tests,  and  the  greatest  distance,  at  which 
the  subject  can  recognize  the  positions  of  the  E's  in  each  line,  is 
determined.  The  results  give  the  average  ratio  of  the  distances  so 
determined  to  the  standard  distances.  There  were  70  cases  in  the 
morning,  giving  an  average  of  1.90,  and  38  in  the  afternoon,  aver- 
aging 1.94.     That  is,  the  difference  is  little  better  than  one  of  chance. 

The  same  subjects,  in  matching  a  series  of  shades  of  colors  with 
a  series  of  tints,  averaged  respectively  11.8  and  11.5  errors,  thus 
favoring  the  morning,  but  only  to  the  chance  degree. 

In  acuity  of  hearing,  as  tested  by  apparatus  devised  by  Mr, 
Bruner  for  the  purpose,  37  men  in  the  morning  showed  an  average 
ability  slightly  inferior  to  that  of  23  men  in  the  afternoon.  The 
numbers  are  too  small  to  make  this  difference  significant. 

2.    Skin-seiisitivity  and  Pressure-sense 

AVhat  work  there  is  here  bearing  on  diurnal  variation  is  best 
discussed  under  the  headings  of  attention  (p.  43  and  Table  XIV.) 
and  fatigue  (p.  79  and  Tables  XXX.,  XXXI.  and  XXXII.). 

3.    Brief  Summary 

No  diurnal  changes  in  sensory  efficiency  are  suggested  by  the 
scanty  data  at  hand,  save  a  possible  low  skin-sensitivity  in  early 
morning. 

III.    Motor  Activities 

1.  Subhuman  Data 

1.  Plaiit  Life.— The  following  statements  are  of  some  interest  for 
comparison  with  human  data.  Saclis  says,  "If  a  plant,  which  has 
been  exposed  to  the  alternations  of  day  and  night,  be  kept  in  dark- 
ness for  a  considerable  time,  the  periodicity  (due  to  light)  may  con- 
tinue for  a  time,  according  to  Pf effer,  as  a  persistent  effect. '  '^  Pierce 
bases  the  following  statements  on  work  by  Sachs:  "The  daily 
periodicity  of  light  and  darkness  is  almost  coincident  with  the 
daily  periodicity  in  growth  rates.  .  .  .  The  rate  of  growth  in  length, 
of  plants  furnished  with  all  the  food  they  need,  will  reach  its  maxi- 
mum about  sunrise  and  its  minimum  about  sunset.  "- 


"^  American  Text-hook  of  Botany,  p.  883.      1882. 
Tlunt  Physiology,  p.  211.      1903. 


COURSE    OP   PSYCHOPHYSIOLOGICAL    EFFICIENCY  15 

2.  Animal  Life.— Hodge  and  Aikins/  experimenting  with  one  of 
the  Protozoa,  found  the  ciliary  activity  of  this  animal,  by  which 
food  is  injected  and  detritus  ejected,  to  be  apparently  without  periods 
of  rest  corresponding"  to  those  of  higher  animals.  This  constancy 
seems  unaffected  by  reproduction,  barometric  pressure,  light,  heat, 
or  sound.  In  their  diagram  of  the  activities  of  the  animal,  the  most 
pronounced  vesicular  and  stalk  contractions  and  reproductive  phases 
appear  to  be  recurrent  in  the  early  morning.  These  are  of  the  same 
order  as  man's  motor  and  reproductive  activities,  while  the  uninter- 
mittent  character  of  the  ciliary  activity  is  what  might  be  anticipated 
when  it  is  remembered  that  this  undifferentiated  functioning  in 
these  unicellular  animals  is  that  which,  in  developed  form,  finds  ex- 
pression in  our  unremitting  circulatory  and  respiratory  perform- 
ances. With  advance  up  the  animal  scale  the  number  of  rhythmic 
activities  slowly  increases. 

2.    Human  Data 

1.  General  Cliaracteristics  of  the  Writer's  Methods  and  Experi- 
ments.—  To  determine  with  scientific  exactness  the  diurnal  course 
of  any  activity  would  require  a  minute  consideration  of  the  subject's 
daily  physical  and  mental  condition,  the  character  of  his  daily  work 
and  habits — as  to  regularity  and  irregularity,  quantity  and  quality — 
and  of  all  external  and  accidental  influences  to  which  he  might  be 
subjected  at  any  period  of  the  day.  It  would  be  impossible  to  ascer- 
tain accurately  all  these  matters,  but  practically  what  we  want  to 
know  is  what  one  does  accomplish  under  just  such  heterogeneous 
circumstances— the  ordinary  conditions  of  life.  Allowances  were 
made  for  several  serious  interruptions,  and  where  illness  occurred 
the  records  were  not  used. 

In  order  to  insure  the  greatest  variety  of  material,  the  data  were 
gathered  not  merely  from  strictly  laboratory  tests,  but  also  from 
those  less  capable  of  exact  measurement  in  standard  terms;  and,  in 
addition,  the  questionnaire  method  was  attempted  and  data  from 
general  and  school  work  utilized.  The  tests  were  applied  extensively 
to  groups  of  subjects  for  one  or  two  days,  and  intensively  to  indi- 
vidual subjects  for  several  weeks.  Some  information  as  to  the  sub- 
jects, periods  and  tests  used  and  as  to  results  and  their  statistical 
treatment  must  be  given. 

Subjects.  The  males  were  seven  in  number,  all  graduate  students 
at  Columbia  University,  ranging  in  age  from  26  to  34,  and  will  be 
referred  to  hereafter  as  I.,  II.-VII.  All  were  conversant  with  and 
practised  in  laboratory  work;  hence  each  acted  as  both  operator  and 

"Daily  Life  of  a  Protozoan,'  Am.  Jour,  of  Psych.,  6:  524-533.     1895. 


16  DIURNAL    COURSE    OF   EFFICIENCY 

subject  in  his  own  case,  after  full  verbal  and  written  instructions  on 
every  test  of  his  series.  The  letter  'A'  will  be  used  to  represent  a 
female  graduate  student,  23  years  old,  engaged  in  intellectual  work 
10  to  13  hours  daily;  'B'  is  a  group  of  young  women  of  Teachers 
College,  ranging  in  age  from  20  to  35.  Both  A  and  B  were  naive 
subjects,  and  their  tests  were  given  by  myself. 

Periods.  The  tests  w^ere  to  be  taken  daily  before  breakfast,  lunch, 
dinner  and  bedtime.  The  actual  times  at  which  they  were  taken 
necessarily  varied  somewhat  for  different  persons,  this  being  one  of 
the  great  practical  difficulties  of  the  problem.  To  get  reliable  results 
one  must  start  with  reliable  subjects,  but  they  are  just  the  ones  who 
can  least  afford  to  distort  their  affairs  daily  for  so  long  a  time.  The 
periods  in  the  tables  are  two  hours  broad  to  allow  classification  of 
the  subjects  together. 

Tests.  Each  subject  went  through  the  tests  for  about  twelve 
days;  the  exact  numbers  will  be  indicated  in  the  following  pages,  to 
which  reference  must  also  be  made  for  detailed  descriptions  of  the 
various  tests.  About  six  sorts  of  tests,  motor  and  mental,  were  given 
to  each  subject,  except  that  subject  I.  (the  author)  took  a  much 
greater  number.  But  the  results  of  some  of  the  tests  admit  of 
double  measurement — for  speed  and  for  accuracy — and  appear  so 
in  the  tables.  The  'number'  given  in  the  second  column  of  some 
tables  has  reference  to  the  trials  at  each  period  and  not  to  the  total 
number  in  the  whole  series. 

Results  and  Statistical  Treatment.  The  results  are  from  whole 
days'  records,  as  already  suggested.^  All  results  are  in  terms  of  the 
average  and  its  probable  error,  the  formula  used  for  calculating  the 
latter  being  ±  0.6745  (ct/V'«),  where  o-  is  the  mean  square  deviation 
and  n  the  number  of  cases.  The  mathematical  chances  are  even  that 
the  average  shown  will  not  vary  from  the  real  (theoretical)  average 
by  more  than  the  limits  of  the  P.E.  It  should  perhaps  be  remarked 
that  it  was  necessary,  though  less  desirable,  to  have  the  higher  fig- 
ures represent  greater  degrees  of  inefficiency  instead  of  efficiency; 
the  larger  the  numbers,  therefore,  the  less  the  efficiency.  Corrections 
were  frequently  made  for  practise  effect.  There  would  be  no  occa- 
sion for  this  if  only  averages  were  sought,  but  it  is  absolutely  re- 
quired when  a  figure  for  their  reliability  is  wanted.  The  method 
used  for  eliminating  the  practise  effect  was  to  make  an  empirically 
graduated  scale  of  allowance  for  the  successive  days,  which  was 
based,  as  to  the  whole  amount,  on  the  absolute  dift'erences  between  the 
initial  and  final  records  and  which  took  advantage,  as  to  graduation, 

'  See  p.  3. 


COURSE    OF    PSYCHOPHYSIOLOGICAL    EFFICIENCY  17 

of  the  established  fact  that  the  effect  of  practise  is  at  first  very  pro- 
nounced and  then  decreases  more  slowly.  There  are  two  assump- 
tions in  the  method :  first,  that  practise  affects  all  the  periods  of  the 
day  equally;  second,  that  any  possible  correction  thus  made  and 
applied  to  all  the  periods  alike  is  legitimate,  however  low  it  reduces 
the  probable  errors,  since  these  will  always  remain  higher  than  if  a 
perfectly  adjusted  and  full  correction  could  be  made.  The  first 
assumption  may  or  may  not  be  true,  but  it  seems  to  me  that  no  excep- 
tion can  be  taken  to  the  second.  Any  correction  of  a  constant  error 
is  almost  sure  to  be  nearer  the  truth  than  any  uncorrected  figure,  as 
it  is  then  transferred  to  the  rank  of  chance  where  elimination  of  its 
influence  b}^  others  is  much  more  likely  to  occur.  When  a  'total' 
average  in  the  tables  refers  to  only  a  few  individuals,  it  should  not 
withdraw  attention  from  the  separate  records  themselves,  where  the 
main  truth  is  then  most  probably  located. 

AVhat  has  been  said  above  refers  also  to  the  mental  tests,  which 
were  taken  by  each  subject  at  the  same  times  as  the  motor  ones.  The 
mass  of  details  to  be  handled  makes  the  briefest  treatment  necessary 
at  every  point,  with  elimination  of  repetitions  as  far  as  possible. 

2.  Actual  Tests  and  Besults— writer's  and  others'.  a.  Speed 
and  Accuracy  of  Movement. — As  a  rather  simple  form  of  movement 
the  subjects  were  required  each  period  to  strike  with  a  pencil  point, 
as  rapidly  as  possible,  200  small  squares  (1  cm.)  arranged  in  10 
columns  of  20  each.  The  time  of  performance  gives  the  measure  of 
speed,  while  the  number  of  squares  missed  roughly  indicates  the 
(in)  accuracy.  None  of  the  subjects  except  the  writer  knew  that 
the  accuracy  was  to  be  considered.  Table  IV.  shows  the  results  and, 
for  convenience  of  comparison,  those  of  a  test  treated  in  the  imme- 
diately following  sub-section. 

A  small  correction  Avas  made  for  practise.  The  greatest  defi- 
ciency appears  at  morning  and  night  periods,  a  dift'erence  that  is 
significant,^  as  seen  by  the  P.E.'s  of  each  average  and  the  uniformity 
of  the  individual  results.  But  the  inaccuracy  maximum  and  mini- 
mum seem  just  the  reverse,  and  this  may  account  for  the  preceding 
differences  entirely  or  in  part. 

The  group  of  young  women,  B,  in  taking  this  test,  were  allowed 
45  seconds  to  strike  200  squares  or  as  many  of  them  as  possible.  The 
results  show  somewhat  the  same  inverse  relation  of  speed  and  accu- 
racy and  the  same  order  of  rate  efficiency  as  the  individual  cases. 
The  improvement  here  might,  however,  be  attributed  to  practise. 

^The  exact  significance  of  a  difference  can  be  found  by  various  formulae: 
see  Thorndike's  Mental  and  Social  Measurements,  p.  145.  But  it  can  be  seen 
well  enough,  often,  by  inspection  of  the  P.E.'s. 


18 


DIURNAL    COURSE    OF   EFFICIENCY 


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COURSE    OF    PSYCHOPHYSIOLOGICAL    EFFICIENCY  19 

Another  sort  of  accuracy  test  in  my  own  case  gave  about  the  same 
result.  The  so-called  hold-and-let-go  method  was  employed  in  a 
twelve-day  series  in  which  a  light  (4  gr.)  wooden  disk  was  snapped, 
on  a  smooth  board,  toward  an  aperture  slightly  larger,  60  cm.  distant. 
This  was  done  ten  times  per  period  each  day  and  the  inaccuracy 
measured  by  the  average  distance  at  which  the  disk  lodged  from  the 
hole.  These  averages  for  the  four  periods,  which  have  large  P.E.'s, 
v/ere  obtained. 

Right  9.3  8.3  7.6  8.7 

Left  12.1  11.4  11.4  12.5 

The  middle  periods  of  the  day  still  remain  better  than  the  morn- 
ing and  evening. 

A  more  complex  movement  was  tested  by  having  several  subjects 
write  the  numeral  words  'one'  to  'twelve'  five  times  each  period  and 
the  time  taken.  Group  B  wrote  as  many  words  as  possible  in  90 
seconds.  The  results,  in  the  above  table,  rather  confirm  the  order  of 
deficiency  in  speed,  as  found  for  the  simpler  movements. 

At  the  Department  of  Psychometry  and  Anthropometry  of  the 
St.  Louis  World's  Fair  many  people  were  subjected  to  various  tests, 
as  above  mentioned,  and  their  records  were  kindly  put  at  my  disposal. 
Only  a  part  of  them  could  be  used  for  the  problem  of  periodicity. 
Two  movement  tests  were  used  which  need  some  description  (see 
right  end  of  Table  V.). 

The  'accuracy'  test  was  devised  by  Dr.  Woodworth  and  consisted 
of  an  equilateral  triangular  piece  of  hard  wood  into  each  apex  of 
which  was  inserted  a  brass  circular  plate  containing  a  central  hole 
6  mm.  in  diameter  and  25  mm.  deep.  These  holes  were  12  cm.  apart 
and  an  electrical  arrangement  was  made  whereby  a  bell  was  rung 
every  time  a  metal  'poker',  a  trifle  less  in  diameter  than  the  holes, 
was  pushed  to  the  bottom  of  any  one  of  them.  The  method  was  to 
hit  the  holes  as  rapidly  as  possible  in  succession,  count  being  kept 
by  the  operator  of  the  record  made  per  minute.  The  accuracy  was 
therefore  measured  in  terms  of  the  rate  at  which  the  accurate  move- 
ment could  be  repeated. 

The  apparatus  for  measuring  the  'rate  of  tapping'  was  also  of 
an  electrical  nature.  A  brass  plate,  about  10  cm.  across,  was  con- 
nected with  a  mechanical  counter^ ;  the  circuit  was  closed  and  the 
counter  moved  forward  one  point  every  time  contact  was  made,  by 
tapping,  between  the  plate  and  a  short  copper  rod,  held  by  the  sub- 
ject.   The  time  for  100  taps  was  taken  by  a  stop-watch. 

'  Kindly  supplied  by  the  C.  H.  Stoelting  Co.,  Chicago,  111. 


20 


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COURSE    OF    PSYCnOPHYSIOLOGWAL    EFFICIEXCY  21 

A  glance  at  the  table  of  results  reveals  five  groups  of  males  and 
three  of  females,  a  separation  made  necessary  by  the  special  condi- 
tions obtaining  in  each.  The  Filipino  'band-men'  are  separated 
from  the  'scouts'  and  'constabulary'  because,  being  musicians,  they 
were  a  highly  selected  group,  and  in  fact,  as  the  results  show,  they 
were  much  quicker  and  more  accurate,  but  much  less  strong,  than 
the  ordinary  soldiers  composing  the  other  groups/  The  first  group 
of  white  males  and  females  comprises  individuals  taken  through  a 
long  series  of  tests  and  measurements,  and  their  records  will  be 
found  much  lower  than  those  of  the  succeeding  groups,  which  were 
taken  under  highly  competitive  conditions  and  only  in  the  activities 
shown.  (4),  of  the  males,  and  (2),  of  the  females,  as  well  as  many 
of  the  Filipino  records  were  taken  by  myself. 

Since  the  morning  and  afternoon  divisions  of  these  groups  were 
composed  of  different  persons,  the  practise  effect,  so  troublesome  in 
most  of  my  other  series,  is  avoided  here.  But  offsetting  that  advan- 
tage is  the  great  difference  between  individuals,  which  raises  the 
variability  of  each  group  and  diminishes  the  reliability  of  the  aver- 
ages. The  P.E.'s  are  indeed  so  large  that  it  did  not  seem  worth 
while  to  insert  them  in  the  table.  While  no  special  significance  can 
be  assigned  to  the  difference  between  the  morning  and  afternoon 
results  of  any  single  group,  the  general  tendency  of  the  whole  table 
seems  plain.  The  number  of  groups  in  which  the  afternoon  records 
surpass  the  morning  is  greater  than  can  reasonably  be  assigned  to 
chance.  This  tendency  to  increased  motor  efficiency  in  the  after- 
noon is  slightly  less  marked  in  the  female  groups  than  in  the  male. 
As  a  whole,  therefore,  these  results  lean  the  same  way  as  those  in  the 
more  intensive  series. 

Use  of  the  same  apparatus  by  myself  gave  the  results  exhibited 
in  Table  VI.  There  were  tv^^o  series  of  tapping  tests.  The  first  was 
for  twelve  days,  in  each  of  which  the  time  was  taken  for  200  taps  at 
ten  different  periods.  In  a  later  one  for  five  days,  the  time  of  200 
taps  was  taken  six  times  at  each  of  seven  periods,  every  200  alter- 
nating with  an  accuracy  test  of  the  time  required  to  ring  the  bell 
100  times. 

The  thing  most  worthy  of  note  in  this  table,  aside  from  the  gen- 
eral agreement  with  the  tendencies  found  above,  is  the  exceptional 
occurrence  and  decisiveness  of  the  maximum  tapping  rate  at  9- 
10  P.M.— less  distinctly  manifested  in  the  case  of  the  right  hand  than 
of  the  left.      The  maximum  of  accuracy  clearly  comes  earlier  in  the 

1  Of  the  soldiers,  all  those  shorter  than  five  feet  or  taller  than  five  feet  six 
inches  are  excluded,  because  it  so  happened  that  a  larger  proportion  of  short 
men  were  tested  in  the  morning  and  of  tall  men  in  the  afternoon. 


22 


DIURNAL    COURSE    OF   EFFICIENCY 


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C0VR8E    OF    PSYCHOPHYSIOLOGICAL    EFFICIENCY 


23 


day  than  the  maximum  of  speed ;  a  shorter  series  of  accuracy  tests, 
with  the  same  subject,  tended  to  place  the  maximum  earlier  than 
4 :30  P.M. ;  there  is  no  doubt  that  it  falls  somewhere  in  the  middle 
portion  of  the  day. 

It  is  obvious  that  the  rating  in  accuracy,  secured  by  use  of  this 
test,  has  some  dependence  on  the  rapidity  of  the  movements  involved. 
To  see  if  any  change  of  order  would  be  efifected,  if  the  factor  of 
speed  were  eliminated,  the  following  trial  was  made.  100  dots, 
1  cm.  apart,  were  arranged  in  ten  (printed)  rows,  both  vertical  and 
horizontal.  By  a  free-hand,  easy  and  uniform  movement,  with  a 
fountain  pen,  these  rows  were  successively  traced  over  both  hori- 
zontally and  vertically,  100  in  each  direction  being  done  at  a  period. 
The  results  are  in  terms  of  the  average  number  of  dots  missed  every 
ten  lines. 

Table  VII. 


No.  of;    7:30  A.M.         9:30 
Rows.  Misses.  P. E.  Mis.  P;E. 


100     0.85  .23 
1001  2.10.47 


11:30 
Mis.  P.E. 


1:30  P.M. 
Mis.  P.E. 


0.80  .19  0.82  .19  1.11  .15  0.98  .2£\  1.10 
1.71  .34  1.92  .43  2.82  .54  1-83  .35\  1.99  .U 


3:30  5:30 

Mis.  P.E.  Mis.  P.E. 


7:30  9:30      1      11:30 

Mis.  P.ET'Mis.  P.E.  Mis.  P.E. 


1.21  .33\1.2i  .S3  l.ZS  .31 
2.72.56  3.03  .50  2.94.5^ 


1.  Horizontal  rows. 


2.  Vertical  rovvs. 


This  test  served  to  confirm  the  other  to  a  considerable  degree, 
doubtless  due  to  the  chief  common  elements— motor  control  and  keen- 
ness, with  quickness  of  sight.  The  main  divergence  is  at  the  second 
period,  which  the  results  make  the  best  of  the  day.  It  is  seen  that 
the  diurnal  curve  is  the  same  for  both  horizontal  and  vertical  rows, 
and  this  helps  to  confirm  periodic  differences  which  the  large  P.E.'s 
made  doubtful,  though  these  are  mainly  due  to  uncorrected  practise 
effect  and  shortness  of  the  series.  The  curve  of  these  figures,  if 
plotted,  closely  resembles  that  of  the  writer's  diurnal  efficiency  as 
subjectively  estimated. 

The  diurnal  couree  of  speed  of  tapping  seems  from  these  results 
to  differ  markedly  from  the  course  of  accuracy  of  movement.  Both 
are  alike  in  showing  a  Iom^  state  of  efficiency  in  the  first  hours  after 
rising,  but  after  that  their  curves  are  nearly  inverse  to  each  other. 
Pure  accuracy  appears  to  reach  a  maximum  in  the  later  morning 
hours,  while  tapping,  in  my  own  case  at  least,  is  at  its  best  in  the 
evening,  when  accuracy  is  about  at  its  worst.  Tapping  also  gives  a 
different  diurnal  curve  from  other  tests  of  speed,  such  as  striking 
squares  or  writing  numerals.  In  explanation  of  this  difference,  it 
is  suggested  that  rapidity  of  tapping,  as  it  requires  a  minimum  of 
control  but  a  maximum  of  neural  excitement,  may  be  expressive 
largely  of  'nervousness.'  If  a  person  is  most  nervous  in  the  evening 
— and  this  agrees  with  my  own  introspection — he  would  accordingly 


24 


DIURNAL    COURSE    OF   EFFICIENCY 


be  quickest  in  tapping  at  that  time,  but  not  most  accurate  in  motor 
control. 

h.  Normal  Muscular  Poiver.  (a)  Small  and  Large  Muscular 
Groups.  Since  many  of  the  conclusions  as  to  muscular  power  and 
fatigue  are  based  on  work  with  small  sets  of  muscles,  it  is  a  question 
of  importance  whether  their  efficiency  at  any  time  is  a  trustworthy 
symptom  of  the  general  muscular  power.  This  will  be  discussed 
incidentally. 

First,  the  Cattell  1903  type  of  spring  ergometer  was  used  by 
subject  I.  to  register  50  contractions  of  the  thumb  and  forefinger  of 
each  hand,  at  every  period,  for  15  days ;  subject  A  made  40  con- 
tractions at  each  period  for  14  days.  However,  the  first  4  days,  in 
both  cases,  were  omitted  for  practise.  The  figures  in  the  table  show 
the  average  number  of  kilos  for  25  and  40  contractions,  for  the 
respective  subjects,  and  the  P.E.'s. 


Table  VIII. 


Subject. 

No.  of  Con- 
tractions. 

8—9  A.M. 

3:30  to  4:30  P.M. 

10:30  to  11:30  P.M. 

Eight.  P.E. 

Left.    P.E. 

Right.  P.E. 

Left.    P.E. 

Eight.  P.E. 

Left.    P.E. 

I.    1st  25.. 
2d  25... 

Average... 

300 
300 

300 

143     1.0 

107    0.9 

125    i.O 

115    0.8 
92    0.9 

103    0.9 

149     1.0 

111    0.8 
130    0.9 

115    0.6 

96    0.7 

105    0.7 

142    0.9 

109    1.1 
125    1.0 

109    0.8 

88    0.9 

98    0.9 

A-@40.. 

400 

126    1.9 

115    2.2 

137    1.7 

125    1.9 

124    2.3 

119    2.2 

With  subject  I.  the  record  was  kept  for  each  half  of  the  50  con- 
tractions. The  table  shows  some  fluctuations,  but  on  the  whole  both 
subjects  show  most  strength  in  the  middle  period,  as  will  be  found 
to  be  generally  true  for  strength.^ 

Lombard,-  working  with  the  Mosso  ergograph  as  modified  by 
himself,  found  the  maximum  power  of  the  flexor  muscles  of  the 
second  finger  to  be  reached  at  10  a.m.  and  10  p.m.  (the  higher  maxi- 
mum) daily,  and  the  minimum  at  4  a.m.  and  4  p.m.  (the  lower  mini- 
mum). He  assigns  the  diurnal  rhythm  of  atmospheric  pressure  as 
the  cause  of  these  changes  in  motor  power.     In  the  same  article  it  is 

^  A  cruder  form  of  test  was  used  by  I.,  involving  the  hold-and-let-go  method 
already  mentioned.  A  lead  ball,  weighing  1)0  cm.,  was  snapped,  or  '  plumped ' 
marble  fashion,  as  far  as  possible  on  a  soft  board,  marked  off  in  centimeters. 
It  registered  its  own  distance  each  time  by  spots,  which  were  erased  after  every 
10  snaps  (the  number  taken  with  both  hands  at  7  a.m.,  12  m.,  5  and  10  P.M, 
for  12  days).  The  results,  in  average  cm.  distances,  were  as  follows:  for  the 
right  hand,  54,  56,  57,  54;  and  for  the  left,  50,  55,  56,  53.  Only  the  greatest- 
least  differences  here  are  of  consequence,  though  the  order  seems  without  doubt 
a  real  one  with  me. 

^ '  Some  Influences  Affecting  the  Power  of  Voluntary  Muscular  Contrac- 
tions,' Jour,  of  Physiol.,  13.      1892. 


COURSE    OF   PSYCHOPHYSIOLOGICAL    EFFICIENCY  25 

found  that,  among  various  influences  increasing  the  power,  food  and 
sleep  are  very  important.  With  this  true  his  morning  maximum 
should  be  much  in  excess  of  the  night  one,  but,  as  a  matter  of  fact,  it 
is  less.  It  is  also  hard  to  see  how  the  slight  barometric  change 
occurring  at  Worcester,  where  the  experiments  were  made,  could  be 
so  decidedly  influential.  Lombard^  also  found  the  diurnal  variations 
in -height  of  knee-jerk  to  be  directly  related  to  the  barometric  pres- 
sure and  inversely  to  the  temperature,  but  mainly  dependent  on 
hunger  and  fatigue,  which  are  highly  depressive  (p.  67).  Here  the 
order  was  a  morning  maximum  and  a  minimum  at  night,  the  decline 
being  irregular;  in  general  the  knee-jerk  was  larger  after  each 
meal  (p.  68), 

Patrizi,-  using  the  Mosso  machine  in  experiments  on. himself  and 
another  adult  male  in  early  morning,  early  afternoon,  evening  and 
midnight,  discovered  the  2:30  p.m.  period  to  be  the  best;  the  evening 
was  better  than  the  morning,  and  the  midnight  result  was  about 
equal  to  that  of  the  morning — an  order  but  slightly  different  from 
that  of  my  own  results.  He  also  quotes  Buch  as  having  found  (with 
the  dynamometer)  a  low  muscular  power  in  the  morning;  greater 
after  luncheon,  and  greatest  after  dinner. 

Harley,^  also  making  use  of  the  Mosso  ergograph,  in  experiments 
on  himself,  found  the  diurnal  variations  under  ordinary  conditions 
to  be:  maximum  about  3  p.m.  and  minimum  at  9  a.m.  (his  experi- 
mental day  was  only  from  9  a.m.  to  8  p.m.),  as  shown  by  Table  IX., 
in  kilogram-meters. 

Table  IX.     Variations  in  Normal  Muscular  Po'^a'er — Ergograph   (after 

Harley)  . 

Hour  9         10        11        12         12345678 

Work  6.2      6.4      8.7      7.0      9.5      8.2      9.9      7.8      8.9      8.7      7.2      8.8 

The  agreement  of  this  result  with  what  has  preceded  is  obvious. 

Christopher'*  employed  the  ergograph  for  tests  90  seconds  long 
every  hour  from  8 :30  a.m.  to  3  :30  p.m.,  one  day,  on  1,127  schoolboys 
and  girls.  More  intensive  tests  w^ere  made  on  four  children  of 
each  sex.    He  concludes  that 

''  Variations  of  Knee-jerk,  etc.,'  Am.  Jour,  of  Psych.,  1:  5-71.     1887. 

-J.  Joteyko,  'Rev.  Generale  sur  la  Fatigue  Musculaire,'  L'Annee  Psych., 
5:   1-54.      1898. 

^ '  Effect  of  Sugar  and  Smoking  on  Muscular  Work,'  Jour,  of  Physiol.,  17. 
1894. 

* '  Report  on  Child-study  Investigation,'  An.  Kept,  of  Bd.  of  Ed.  of  Chicago. 
1898-1899. 


26 


DIURNAL    COURSE    OF   EFFICIENCY 


1.  The  extremes  of  endurance  and  fatigtie  are  greater  in  the 
morning  than  in  the  afternoon. 

2.  Strength  is  not  as  great  in  the  afternoon,  but  is  better  sus- 
tained than  in  the  morning. 

3.  In  children  the  intellectual  capacity  varies  as  the  physical 
condition. 

Smedley^  repeated  the  experiments  on  six  boys  and  six  girls  of 
another  school  and  practically  confirmed  the  other  work,  as  reference 
to  Fig.  3  will  indicate. 


Hou.t  0^  tKe  liau.  — 

A../M.  T,m. 

i  3ct  T 


.5  it» 

c 
<» 

.6    220 

r 


Solid  lint  =  o-yerflu-^e  Xt-coti  of  (in  t>«iy'iU  ej  OlUoti  StKool. 
3relt«R  t.  i       "       «  ••         ••      f       •.         ..  •.  •''    , 


These  results  suggest  that  fatigue  may  be  a  more  influential  factor 
with  children  than  with  adults  and  may  modify  the  diurnal  curve 
accordingly.     This  whole  matter  will  be  treated  at  length  later. 

Oseretzkowsky  and  Kraepelin,-  using  Mosso's  type  of  ergograph, 
found  that  the  average  height  of  contraction  (measuring  the  amount 
of  performance)  was  greater  at  2  p.m.;  but  the  number  of  contrac- 
tions (measuring  the  endurance)  at  10  a.m.  These  experiments, 
being  made  only  at  the  hours  named,  contribute  only  confirmatory 
evidence  to  what  has  already  been  produced. 

Storey^  reports  work,  with  a  modification  of  this  type  of  machine, 
on  students  of  Stanford  University,  number  not  given.      The  first 

^ '  Report  on  Child-Study  Investigation,'  An.  Rept.  of  Bd.  of  Ed.  of  Chicago. 
1899-1900. 

^ '  Ueber  die  Beeinflussung  der  Muskelleistung  durch  verschiedene  Arbeits- 
bedingungen,'  Psych.  Arbeit  en,  3:  643  seq.     1901. 

^  Some  Daily  Variations  in  Height,  Weight  and  Strength,'  Am.  Phys.  Ed. 
Rev.,  6.      1901. 


COURSE    OF   PSYCHOPHYSIOLOGICAL    EFFICIENCY 


27 


series  was  from  8  a.m.  to  6  p.m.  and  shows  the  maximum  at  4  p.m. 
and  minimum  at  noon— but  slightly  below  the  8  a.m.  figure.  In  a 
second  series — details  lacking — from  7  a.m.  till  11  p.m.,  the  highest 
point  occurred  at  9  p.m.  and  lowest  at  7  a.m. 

Subsequently/  for  himself,  he  found  that  "there  is  a  normal 
decrease  in  ability  to  do  muscular  work  between  2  and  5  p.m." 
(p.  193).  This  must  be  a  misprint,  for  at  another  place  he  says 
"the  morning  max.  comes  at  or  near  10  a.m  and  the  afternoon  max. 
at  or  near  4  p.m.,"  and  this  is  borne  out  by  his  tables,  which  are, 
however,  not  always  clear. 

Very  recently-  he  has  made  an  extended  study  of  the  matter 
which,  on  the  whole,  confirms  his  earlier  results  and  conclusions. 
Half  the  article  describes  the  rather  complex  apparatus  used— his 
own  modification  of  the  Lombard  ergograph,  employing  weight  or 
spring  resistance,  as  desired.  His  method  of  exhibiting  results  is 
open  to  criticism,  for  only  the  roughest  comparison  of  groups  is 
possible,  and  that  not  of  the  best  sort.  How  much  was  gained  or 
lost  is  usually  the  most  essential  thing  to  know.  The  results  show 
the  number  of  times  that  gains  or  losses  in  power  were  found  for 
the  successive  hours,  when  each  was  compared  with  the  preceding. 
The  unequal  numbers  of  trials  at  the  different  periods  show  that  the 
false  assumption  Avas  entertained— alluded  to  before^  as  made  by 
many  authors— that  incomplete  records  of  some  of  the  days  repre- 
sented give  reliable  data  for  such  relational  procedure  as  the  prob- 
lem involves.  Storey  himself,  a  well-trained  subject,  comes  first 
in  the  table.  A  language  student,  21  years  old,  taking  no  regular 
exercise,  gave  the  results  in  the  second  division  of  the  table.  A  law 
student  and  athlete,  21  years  old,  is  reported  in  the  third  section, 
while  three  adult  mechanics  gave  the  results  of  the  last  section. 


Table  X.     Compabison 

OF 

Hourly  Ergographic  Records- 

—After 

Storey. 

No.  of 
Subjects. 

6-7 

7-8 

8-9 

9-10 

10-11 

11-12  12-1 

1 

1-2    2-3 

3-4 

4-5 

5-6 

6-7 

7-8 

8-9 

9-10 

1 

Gaining. 

6 

24 

16 

12 

4 

5 

11    28 

14 

2 

3 

5 

3 

0 

Losing. 

0 

1 

5 

4 

20 

1 

3i    1 

6 

16 

17 

1 

3 

5 

1 

Gaining. 
Losing. 

6 
2 

6 

1 

9 
0 

! 

5 
3 

5 
5 

2 
8 

1 
4 

1 

Gaining. 

11 

8 

5; 

12 

10 

Losing. 

1 

6 

10 

3 

4 

3 

%  of  gains. 

161 

52 

21  j 

3 

%  of  losses. 

1 

33' 

6 

15 

48 

^ '  Daily  Variation  in  the  Power  of  Voluntary  Muscu'ar  Contraction,'  Am. 
Phys.  Ed.  Rev.,  7.      1902. 

^  Studies  in  Voluntary  Muscular  Contraction,  Stanford  Press,  pp.  60. 
1904. 

^  See  above,  p.  2. 


28  DIURNAL    COURSE    OF   EFFICIENCY 

AVith  the  Upham  dynamometer  Storey  then  tested,  in  all,  several 
hundred  Stanford  students  by  one  grip  before  and  one  after  an 
hour's  gymnasium  practise  in  classes  at  10-11  a.m.  (1,653  records 
for  each  hand)  ;  11-12  a.m.  (1,772)  ;  3-4  p.m.  (1,366)  ;  4-5  p.m. 
(1.990)  ;  5-6  P.M.  (2,726).  His  main  object  was  to  ascertain  the 
influence  of  gymnasium  work  on  motor  power,  but,  considering  this 
work  a  constant  factor,  the  above  periods  can  be  compared.  The 
results  are  thus  stated :  ' '  there  is  evidence  of  a  morning  period  of 
muscular  ability  between  10  and  11  a.m.;  a  subsequent  diminution 
between  11  and  12;  a  tendency  to  rise  between  3  and  4  p.m.;  about 
the  same  condition  between  4  and  5 ;  and  finally  there  is  evidence  of 
a  tendency  to  lose  power  between  5  and  6  p.m."  (p.  49). 

This,  he  truly  saj^s,  verifies  all  the  preceding  work.  He  fails  to 
call  attention  to  the  early  morning  degree  of  inefficiency,  though  its 
presence  is  indicated  by  the  high  gains  at  the  8-9  and  9-10  periods. 
These  results  being  in  such  a  form  as  to  give  no  definite  idea  of  the 
real  quantitative  difference  of  efficiency  at  the  different  hours  can 
not  be  closely  compared  with  the  work  of  other  authors,  but  the 
divergence  between  his  results  and  mine  lies  almost  wholly  in  the 
extent  of  the  noon  and  night  drops.  As  to  the  general  form  of  the 
diurnal  curve,  they  are  alike. 

The  present  writer  also  tested  the  strength  of  the  grip,  first  using 
Collin's  oval  dynamometer.  This  instrument  was  also  used  in  a  set 
of  leg-back  tests,  to  be  treated  very  soon.  For  convenience  both 
results  are  incorporated  in  Table  XI. 

These  figures  point  rather  consistently  one  way,  being  similar  to 
Storey's  save  in  the  particulars  mentioned  above. 

My  own  individual  order,  of  an  early  minimum  and  late  after- 
noon maximum,  is  placed  beyond  all  doubt  by  three  other  series. 
The  first  was  for  30  days  in  autumn,  under  great  regularity  of 
external  and  subjective  conditions.  Five  grips  at  each  of  7  periods 
were  taken.  The  second  was  also  for  30  days,  morning  and  night, 
2  grips  at  each.  The  third  was  for  12  days,  11  periods  and  2  grips 
at  each.  The  last  two  were  taken  with  the  Narragansett  dynamom- 
eter, registering  higher  than  the  Collin 's  instrument,  which  was  used 
in  the  first  series.  The  great  amount  of  material  secured  enabled 
me,  however,  to  transmute  the  results  of  the  one  into  the  unit  of  the 
others  with  but  slight  absolute  error,  that  would  not  at  all  affect 
the  relative  standing  of  the  periods.  To  eliminate  practise  effect, 
the  first  ten  days'  records  of  the  first  two  series  are  omitted;  no 
allowance  was  made  in  the  third,  which  immediately  succeeded  the 
second  in  point  of  time  but  stands  second  in  the  table. 


COURSE    OF   PSYCHOPHYSIOLOGICAL    EFFICIENCY 


29 


Table   XII.      Musculab   Power — Hand   Dynamometer. 


Subject  I. 

No.  of 

7 :  00  A.M. 

8 :  30  A.M. 

10:00  A.M. 

11:30  A.M. 

1-1 :  30  P.M. 

3:00   P.M. 

Grips. 

Kilos  P.E. 

Kilos    P.E. 

Kilos  P.E. 

Kilos  P.E. 

Kilos  P.E. 

Kilos  P.E. 

f 

100 

60.7  0.17 

63.5  0.16 

64.9  0.18 

Right...  j 

24 
40 

60.8  0.27 
60.2  0.23 

6.30  0.26 

65.2  0.23 

66.2  0.22 

66.1  0.32 

66.2  0.28 

r 

100 

56.6  0.18 

59.3  0.18 

60.7  0.18 

Left 

24 
40 

52.2  0.36 
54.1  0.19 

54.1  0.30 

56.0  0.33 

58.2  0.28 

58.3  0.37 

58.1  0.32 

Subject  I. 

No.  of 

4-4 :  30  P.M. 

6:00    P.M. 

7-7:30  P.M. 

9:00  P.M. 

10-10:30P.M. 

11-12:00P.M. 

Grips. 

Kilos  P.E. 

Kilos  P.E. 

Kilos  P.E. 

Kilos  P.E. 

Kilos  P.E. 

Kilos  P.E. 

f 

100 

66.2  0.19 

63.7  0.18 

61.7  0.17 

60.7  0.21 

Right...  j 

24 

40 

67.3  0.25 

69.0  0.30 

67.1  0.22 

66.0  0.23 

64.2  0.25 

63.9  0.33 

r 

100 

61.7  0.20 

59.5  0.17 

58.0  0.17 

56.6  0.22 

Left j 

24 
40 

59.2  0.24 

60.1  0.22 

58.0  0.35 

56.3  0.31 

54.1  0.31 

57.7  0.19 

Attention  is  here  called  to  Table  V.,  showing  various  groups  of 
males  and  females  tested  as  to  forearm  strength.  It  will  be  noted 
that  the  men  did  almost  uniformly  better  in  the  afternoon  than  in 
the  morning,  while  the  females  were  about  evenly  divided.  How 
these  results  are  to  be  construed  has  already  been  mentioned  and 
needs  no  fuller  comment  at  this  point. 

The  larger  muscular  groups  are  not  so  readily  tested.  At  an 
international  meeting  of  the  University  Physical  Directors  at  Prince- 
ton, in  December  of  1903,  an  attempt  at  agreeing  on  the  best  gym- 
nasium methods  of  testing  general  muscular  efficiency  was  unsuc- 
cessful, and  it  was  decided  to  temporarily  continue  the  old  ones  with 
certain  modifications.  This  suggests  the  difficulty  of  getting  ade- 
quate tests. 

Floor  Dip.  This  was  meant  to  test  the  arm  muscles  mainly, 
and  consisted  in  extending  the  (rigid)  body  parallel  with  the  floor, 
on  toes  and  hands,  and  then  alternately  raising  and  lowering  it  by 
the  arms  as  rapidly  and  as  often  as  possible,  efficiency  being  measured 
by  the  number  of  times  it  was  thus  completely  raised.  The  tests 
v/ere  on  myself  for  twelve  days,  but  the  first  three  w^ere  omitted  and  a 
small  correction  made  on  the  rest  for  practise.  The  results  are 
decisive  for  the  periods  shown. 

7  A.M.,  17.2  (P.E.,  .15) ;  12  M.,  21.3  (.34)  ; 

5  P.M.,  22.6  (.28)  ;  10  P.M.,  19.3  (.15). 

Floor  Squat:  a  test  for  leg  muscles  in  w^hich  the  subject  alter- 
nately squatted  and  raised  himself  100  times  as  rapidly  as  possible. 
An  extended  effort  to  measure  the  deficiency  present  by  the  shorten- 
ing of  the  time  the  subject  could  hold  his  breath  after  the  exercise, 
3 


30 


DIURNAL    COURSE    OF   EFFICIENCY 


P4 


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COURSE    OF   PSYCHOPHYSIOLOGICAL    EFFICIENCY  31 

or  by,  the  increase  in  pulse  rate,  proved  fruitless.  Then  forty-pound 
dumb-bells  were  held  in  the  hands  and  quick  fatigue  secured  by 
squatting:  as  before,  in  a  short  series.  The  results  were  too  meager 
for  quantitative  expression  but  quite  similar  in  tendency  to  those 
of  the  floor  dip  for  arm  muscles. 

Hand-foot  Dynamometer:  designed  to  test  combined  arm,  back 
and  leg  strength.  It  is  made  up  of  the  Collins  oval  dynamometer, 
having  a  kilo  scale  for  use  when  the  instrument  is  pulled  endwise 
and  equipped  with  the  necessary  handle  and  foot  attachments  for 
pulling.  A  short  length  to  the  whole,  14  inches,  insured  full  use 
of  the  leg  muscles  as  the  subject  sat  on  the  floor  and  pulled.  The 
operations  were :  right  hand  and  foot,  left  hand  and  foot,  and  finally 
both  hands  and  feet,  three  times  each  period.  The  results  are  shown 
in  Table  XI.,  while  Table  V.  gives  some  results  for  two  Filipino 
groups,  with  whom  Tiemann  's  pulling  apparatus  was  used,  also  regis- 
tering in  kilos.  There  is  no  radical  discrepancy  between  these  and 
preceding  results.  Though  the  P.E.  is  sometimes  large,  it  is  clear 
from  the  whole  course  of  the  figures  that  the  middle  of  the  day,  in- 
cluding the  afternoon,  is  a  time  of  greater  muscular  strength  than 
either  morning  or  evening. 

The  curve  of  strength  efficiency  seems,  therefore,  well  established 
for  the  following  course,  and  this  probability  will  be  strongly  rein- 
forced below  by  further  data :  a  beginning  minimum  in  early  morn- 
ing, a  fairly  rapid  rise  till  11,  a  level  or  slight  decline  till  1  p.m. 
(±:  1  hour),  an  increase  to  the  maximum  at  5  (ih  1  hour),  thence 
a  fall  till  bedtime.     Explanation  of  this  is  attempted  in  Part  D. 

(6)  Comparative  Fmictioning  of  Muscle  Groups.  As  to  whether 
the  work  of  very  small  groups  can  be  taken  as  indicative  of  the  gen- 
eral muscular  condition,  an  assumption  long  and  often  made  with 
little  attempt  at  proof,  it  appears  from  the  above  tables  that  the 
assumption  is  in  reality  well  founded.  In  order  to  avert  confusion, 
attention  was  not  called  to  this  point  in  passing,  nor  to  the  one  suc- 
ceeding, and  their  verification  must,  therefore,  be  retrospective  on 
the  part  of  the  reader. 

(c)  Bilateral  Symmetry.  Regarding  this  matter,  a  review  of 
Tables  V.,  VI.,  VIII.,  XI.  and  XII.  will  disclose  the  fact  that, 
although  fluctuations  occur,  yet  as  a  whole  the  figures  show  the  same 
general  course  of  efficiency  for  both  sides  of  the  body.  The  other 
evidence  obtained  agrees  on  this  point.  Lombard^  with  the  ergo- 
graph  noted  that  the  strength  may  be  greater  on  one  side  when 
least  on  the  other,  but  that  'the  major  variations  occur  simultane- 

'^^  Fatiguing  Voluntary  Work,'  Jour,  of  Physiol.,  14.      1893. 


32  DIURNAL    COURSE    OF   EFFICIENCY 

ously  on  the  two  sides'    (p.  114),  and  Storey,  in  a  work  already 
cited,  with  many  subjects  found  the  same. 

c.  General  Motor  Control.  Experiments  with  the  ataxiagraph 
to  determine  relative  steadiness  in  standing  for  different  times  of 
day,  and  with  the  automatograph  to  determine  changes  in  involun- 
tary movement,  were  planned  but  could  not  be  carried  out  for  lack 
of  time,  though  the  author  is  convinced  by  rough,  tentative  tests  in 
balancing,  etc.,  that  the  field  is  fruitful  for  this  problem  and  would 
throw  light  on  the  other  results. 

d.  Complex  Motor  Activity.  Of  course  there  is  no  jump  be- 
tween the  following  and  Avhat  has  preceded.  Attempt  was  made  to 
get  data  on  activities  of  a  more  comprehensive  character,  first  by 
means  of  a  questionnaire  designed  particularly  for  physical  directors 
and  athletes,  and  containing  questions  as  to  what  their  experience 
would  lead  them  to  say  on  the  matter  of  recurrent  periods  of  varying 
ability,  and  their  objective  grounds  for  the  opinion.  The  few  replies 
that  have  been  received  are  suggestive. 

Mr.  J.  G.  Lathrop,  Physical  Director^  of  Schools  at  Southboro, 
Mass.,  says:  "I  have  never  considered  it  possible  for  me  or  any  one 
under  me  to  do  as  good  performances  in  the  morning  as  in  the 
afternoon  and  that,  so  far  as  I  know,  is  the  experience  of  others. 
This,  I  consider,  applies  to  any  form  of  athletic  work." 

Dr.  G.  L.  Meylan,  Medical  Director  of  Columbia  Gymnasium, 
after  long  experience  as  physical  director,  corroborates  these  words 
of  Mr.  Lathrop.  Mr.  Davis,  his  assistant,  holds  the  same  decided 
opinion,  and  both  describe  various  performances  in  substantiation 
thereof. 

Miss  Louisa  Smith,  Director  of  the  Bryn  Mawr  Gymnasium,  re- 
plied thus :  ' '  We  have  athletics  only  in  the  afternoon  and  no  compari- 
sons can  be  made.  But  I  have  noticed  this :  when  we  used  to  have  both 
afternoon  and  evening  classes,  the  students  of  the  afternoon  classes 
did  the  better  work  in  educational  gymnastics.  In  our  physical 
examinations,  too,  I  have  noticed  that  those  strength  tests  that  are 
taken  in  the  early  part  of  the  day  average  better 'than  those  taken 
between  9  and  10  in  the  evening."  Here  we  find  the  same  as  set 
forth  above  for  females. 

Mr.  C.  H.  Robinson,  Harvard  athlete,  21  years  old,  submits  this : 
"Last  winter  [1903]  I  competed  in  the  shot-put  at  the  Boston 
Athletic  Association  games  and  the  best  distance  I  could  get  was 
40  feet.  These  games  came  Saturday  night.  On  the  Monday  fol- 
lowing I  returned  to  my  practise  in  the  afternoon  and  easily  reached 

^  Now  track-team  coach  at  Harvard  University. 


COURSE    OF   PSYCHOPHYSIOLOGICAL    EFFICIENCY  33 

44  feet.  I  have  found  this  same  fact  true  when  I  worked  in  the 
morning."  He  thinks  the  time  of  the  maximum  is  determined  by 
that  of  practise — which  is  only  partly  true. 

Mr.  T.  G.  Meier,  another  Harvard  athlete,  23  years  old,  says 
that  he  "has  never  noticed  any  particular  difference  between  morn- 
ing, afternoon  and  night  scores";  but  mentally  the  morning  seems 
best,  with  periods  of  lesser  alertness  after  lunch  and  dinner,  and 
then  an  efficient  one  from  8  p.m.  to  12  m.  This  case  must  be  noted 
as  an  apparent  exception. 

Under  the  present  heading  will  also  be  discussed  certain  observa- 
tions of  manual  labor  in  factories,  made  by  the  author  at  various 
times  through  several  months.  The  main  results  are  given  in  Table 
XIII.,  which  reveals  also  the  chief  conditions.  But  some  words  must 
be  added  in  fuller  description  of  each  group. 

The  first  group^  is  the  most  noteworthy,  by  reason  of  the  regu- 
larity of  the  work,  the  basis  of  pay,  and  the  number  of  hours  per  day. 
Its  members  were  all  experienced  stitchers  except  the  last,  in  whose 
case  a  correction  was  necessary  for  practise  effect.  They  worked  at 
top  speed,  presumably,  as  long  as  the  material  was  supplied  by  the 
'gathering  machines',  which  was  about  45  or  50  minutes  out  of  each 
hour.  That  is,  all  were  obliged  to  stop  these  few  minutes  while  the 
supply  'piled  up'  for  the  succeeding  hour's  run.  At  12,  5  and  9  p.m. 
they  worked  only  half  an  hour.  Other  than  this  the  individual  stops 
were  insignificant.  One  was  sick  four  days,  another  transferred  to 
other  work  for  a  day,  etc.,  so  that  although  observations  were  con- 
tinued eleven  days  no  one  is  reported  for  the  full  time.  The  first 
day's  work  was  disregarded  entirely,  as  it  was  found  to  be  much 
affected  by  the  initial  experience  of  being  observed.  The  same  was 
true  with  the  second  group.  Ordinarily,  120  magazines  at  a  time 
were  given  to  each  worker,  while,  on  my  part,  the  time  required  to 
do  this  number,  or  any  multiple  of  it,  was  taken  just  as  often  as  it 
could  be  caught  exactly,  and  subsequently  reduced  to  the  form  shown 
in  the  table. 

In  the  second  group  the  first  two  girls  were  experienced  and 
piece-workers;  the  rest  were  inexperienced  and  worked  partly  by 
piece  and  partly  by  time,  hence  it  was  useless  to  attach  P.E.'s  to 
their  averages.  When  paid  by  the  thousand,  they  did  from  30  to 
60  per  cent,  more  than  when  paid  by  the  day.  Through  the  kind- 
ness of  the  foreman*  the  work  was  given  to  them  in  even  hundreds; 
otherwise  it  would  have  been  impossible  to  get  correct  records  of 

^  The  work  was  the  binding  of  a  900,000  edition  of  Everybody's  Magazine 
by  the  Trow  Directory  Co.,  New  York  City. 

*  These  observations  were  made  at  Dennison  and  Sons,  New  York  City. 


34 


DIURNAL    COURSE    OF   EFFICIENCY 


more  than  two  girls  at  a  time.  In  fact,  several  days  were  devoted  to 
the  first  two  before  the  above  arrangement  was  instituted,  and  tab 
was  kept  of  the  individual  holders  made.  After  that  the  time  per 
100,  for  each  of  the  eight,  was  taken  as  frequently  as  it  could  be 
caught,  together  with  the  corresponding  time  of  day.  More  labor 
than  for  the  first  group  was  required  to  reduce  these  data  to  a  uni- 
form basis.  The  ten-minute  basis  was  chosen  to  agree  with  the  first 
group,  where  it  had  been  selected  to  avoid  the  use  of  four-place 
numbers  for  the  hour.  During  most  of  the  time  the  work  was  dis- 
tributed to  the  workers  by  the  author,  which  insured  better  control 
of  the  conditions. 

The  third  group  covers  cases  where  reliable  records  for  only  one 
or  two  days  were  secured.'  In  the  pursuit  of  this  phase  of  the 
general  problem  much  valuable  time  was  wasted  in  seeking  oppor- 
tunity for  suitable  observational  work,''  but  the  trouble  did  not  end 
there.  Some  people  naturally  object  to  being  watched  so  closely 
and  especially  w^hen  on  time-work.  This  would  not  be  in  evidence 
till  after  the  first  day.  In  several  instances  records  were  thrown 
away  for  wilful  'soldiering'.  To  make  these  results  from  various 
sorts  of  work  comparable  it  Avas  necessary  to  treat  them  as  indicated 
in  the  table.  That  is,  -f-  11  for  the  first  subject  means  that  she  was, 
between  8  and  9  a.m.,  11  per  cent,  above  her  average  efficiency  for 
the  whole  time  observed. 

Table  XIII.     Female  Industrial  Labor. 

I.  Magazine  Wire-stitching.  — Average  Number  Done  per  Each  10  Minutes 
,  of  the  Hour.  — Piece-rate  Basis  of  Pay. 


8-9 

A.M. 

9-10 

10 

-11 

11 

-12 

12-1 

(12:30) 

Subj. 

Age. 

Days. 

Nights. 

No. 

P.  E. 

No. 

P.  E. 

No. 

P.  E. 

No. 

P.  E. 

No. 

P.  E. 

1. 

27 

9 

4 

148 

1.38 

156 

1.09 

158 

0.47 

155 

1.39 

157 

1.06 

2. 

24 

9 

3 

144 

1.42 

156 

1.54 

155 

2.71 

155 

2.32 

152 

1.79 

3. 

20 

10 

5 

146 

1.81 

153 

1.43 

153 

0.88 

150 

1.26  158 

1.23 

4. 

32 

10 

3 

138 

1.03 

149 

0.79 

150 

1.04 

156 

1.11 

156 

1.51 

5. 

20 

9 

3 

128 

2.62 

140 

2.33 

142 

2.02 

141 

2.32 

149 

1.43 

6. 

26 

10 

4 

109 

0.85 

110 

0.71 

108 

1.14 

109 

0.82 

110 

1.05 

7. 

23 

5 

3 

110 

1.24 

115 

1.59 

119 

2.48 

111 

2.28 

118 

2.34 

8. 

19 

7 

3 

111 

1.67 

114 

1.94 

118 

2.02 

117 

2.41 

115 

2.79 

Av. 

24 

8.6 

3.5 

129 

1.59 

137 

1.43 

138 

1.59 

137 

1.74 

139 

1.65 

1  For  these  records  I  am  mainly  indebted  to  J.  English  and  Sons  and 
Dennison  and  Sons,  New  York  City. 

2  What  obstacles  one  encounters  on  this  score  is  suggested  in  the  following: 
5  each  of  apparently  the  best  representatives  of  20  lines  of  manufacture  were 
selected  and  a  carefully  written  letter  sent  to  each,  stating  aims  and  needs, 
together  with  stamped  addressed  return  envelope.  Of  these  100  letters,  6  were 
returned  unopened,  7  unfavorably  answered,  9  favorably  answered,  and  78 
ignored  entirely.  Of  the  9,  5  factories  were  distant  from  New  York,  3  were 
unfit  for  the  work,  and  2  were  used. 


COURSE    OF   PSYCHOPHYSIOLOGICAL    EFFICIENCY 


35 


1-2  P.M.   1     2 

-3 

3-4 

1-5 

5-6  (5:30) 

Subj. 

Age. 

Days. 

Nights. 

No. 

P.  E.   No. 

P.  E. 

No. 

P.  E. 

No. 

P.  E. 

No.   P.  E. 

1. 

27 

9 

4 

156 

0.90  158 

1.42 

152 

0.81 

153 

1.64 

154   1.71 

2. 

24 

9 

3 

157 

2.62  162 

1.23 

158 

2.90 

162 

2.91 

154  1.79 

3. 

20 

10 

5 

156 

1.02  \  156 

1.53 

151^ 

1.56 

153 

1.51 

156  1.11 

4. 

32 

10 

3 

155 

1.19 

151 

1.01 

147 

1.07 

152 

1.00 

151  0.97 

5. 

20 

9 

3 

143 

2.40 

144 

2.21 

143 

1.87 

143 

2.43 

147  2.60 

6. 

26 

10 

4 

113 

0.97  113 

0.85 

113 

0.62 

108 

0.78 

106  1.07 

7. 

23 

5 

3 

126 

1.24  125 

2.27 

121 

2.49 

114 

3.23 

112  3.42 

8. 

19 

7 

3 

111 

1.57 

112 

1.66  112 

1.82 

112 

2.28 

105  1.77 

Av. 

24 

8.6 

3.5 

140 

1.49 

140 

1.52 

137 

1.64 

137 

1.97 

136  1.80 

Age. 


27 
24 
20 
32 
20 
26 
23 
19 


24 


9 
9 

10 

10 

9 

10 

5 

7 


8.6 


Nights, 


4 
3 
5 
3 
3 
4 
3 
3 

3.5 


6-7 
No.      P.  E. 


157 

163 
156 
160 
148 
117 
121 
110 


1.12 
2.86 
1.58 
3.82 
3.48 
2.06 
2.51 
1.78 


141  2.40 


No.   P.  E. 


158 
160 
156 
155 
148 
116 
115 
118 


1.01 
0.62 
1.72 
2.41 
2.29 
2.00 
2.39 
1.39 


141  1.73 


8-9 
No.   P.  E. 


163 
158 
157 
152 
142 
116 
115 
114 


0.93 
0.00 
1.31 
1.12 
2.61 
1.60 
2.35 
2.83 


140  1.60 


9-10  (9:30) 
No.   P.  E. 


164 
159 
157 
162 
140 
121 
111 
113 


1.28 
0  62 
1.63 
3.75 
3.56 
1.92 
2.43 
2.71 


141      2.24 


II.  Making  Paper  Coin-cases.  —  Average  Number  Done  per  Each 
10  Minutes  of  the  Hour. 


Subj. 

Age. 

Days. 

Pay 

8-9 

A.M. 

9-10 

10-11 

11 

-12 

12-1 

(12:30) 

No. 

P.  E. 

No. 

P.  E. 

No. 

P.  E. 

No. 

P.  E. 

No. 

P.  E. 

1. 

18 

10 

Piece 

94 

1.66 

97 

1.21 

94 

1.29 

92 

1.42 

89 

1.90 

2. 

16 

9 

74 

2.10 

79 

1.14 

76 

0.81 

72 

0.56 

71 

1.99 

3. 

16 

6 

47 

48 

46 

46 

47 

4. 

17 

5 

ns  CQ 

61 

61 

62 

58 

61 

5. 

16 

4 

iV. 

49 

50 

48 

43 

39 

6. 

16 

3 

<u  S 

50 

41 

43 

45 

45 

7. 

15 

5 

S^H 

52 

50 

49 

50 

52 

8. 

14 

o 

fM 

40 

43 

41 

39 

36 

Av. 

16 

5.6 

58 

59 

57 

56 

55 

Subj. 

Age. 

Davs. 

Pay 
Basis 

1-2  P.M. 

2-3 

3-4 

4-5 

5-6 

(5:30) 

No. 

P.  E. 

No. 

P.  E. 

No.   P.  E. 

No.   P.  E. 

No. 

P.  E. 

1. 

18 

10 

Piece 

97 

1.56 

97 

2.11 

94   1.98 

90   1,16 

87 

1.49 

2. 

16 

9 

(( 

73 

1.73 

70 

1.34 

70   1.42 

73   1.55 

77 

1.64 

3. 

16 

6 

CO 

51 

50 

44 

43 

42 

4. 

17 

5 

59 

53 

51 

50 

52 

5. 

16 

4 

49 

47 

44 

43 

42 

6. 

16 

3 

%a 

48 

47 

46 

44 

34 

7. 

15 

5 

^,H 

47 

44 

45 

45 

42 

8. 

14 

3 

P4 

41 

40 

43 

36 

33 

Av. 

16 

5.6 

58 

56 

55 

53 

51 

36 


DIURNAL    COURSE    OF   EFFICIENCY 


III.  Numbering  Checks  and  Ledger-lines.  — Hourly  Per  Cents.  Above 
or  Below  the  Day's  Average  Rate. 


8-9  A.M. 

9-10 

10-11 

11-12 

1-2  P.M. 

2-3    ■ 

3-4 

4-5 

Subj. 

Age. 

Days. 

Nights. 

No. 

No. 

No. 

No. 

No. 

No. 

No. 

No. 

1. 

24 

2 

03 

+  11 

+   9 

+  4 

—  7 

—  15 

+    1 

—    6 

+   3 

2. 

19 

1 

^ 

—  19 

-10 

0 

+  14 

+  18 

+   9 

+    2 

—  14 

3. 

21 

1 

+    8 

+  10 

+   6 

+   6 

—  12 

—  2 

—  12 

—  4 

4. 

32 

1 

s 

—    4 

—  3 

—  2 

+   4 

+    6 

—  3 

■4-   3 

—  1 

5. 

18 

1 

H 

—  12 

+  16 

+  32 

+  31 

+    9 

—  18 

—  25 

-32 

6. 

36 

2 

Piece 

—    6 

—  0 

+  6 

+•   3 

0 

0 

—  3 

0 

Av. 

25 

1.3 

—    3.7 

+   3.7 

+   7.7 

+  8.7 

+    1.3 

—  2.2 

—  6.8 

—  8.0 

In  considering  these  figures,  if  one  were  to  look  only  at  the  total 
averages,  it  would  not  be  very  troublesome  perhaps  to  read  off  what 
they  most  probably  meant.  That  would  not  exhaust  the  facts, 
however,  and  might  be  misleading.  From  this  standpoint  it  might 
be  said  that  the  first  group  shows  increasing  efficiency  till  3  p.m., 
then  a  decrease  till  5 :30,  then  a  marked  recovery  and  maximum  rate 
till  9  :30 ;  in  the  case  of  the  second,  a  morning  maximum,  followed 
by  decrease  till  12  :30,  then  a  sharp  recovery  and  a  succeeding  grad- 
ual descent ;  and  in  the  third,  a  gradual  increase  to  a  noon  maximum, 
and  then  a  more  rapid  decrease  to  an  evening  minimum.  Of  the 
individual  curves  of  a  group,  a  rather  large  proportion  follows  the 
respective  group  curve.  Thus,  1,  2,  6,  7,  in  I. ;  1,  4,  5,  7,  8,  in  II. ; 
and  2,  5,  6,  in  III.  This  is  more  evident  in  the  plotted  curves,  of 
which  only  those  of  the  wire-stitchers  were  drawn. 


A..M 


F^^M. 


Fig.  4.      Magazine  Wire-stitching  by  Females — see  Section  1  of  Table  XIII. 

What  specifically  need  attention  are  the  fluctuations  occurring  at 
the  first,  fifth,  tenth  and  fourteenth  periods.  In  the  first,  17  sub- 
jects show  low  efficiency  and  only  5  show  a  relatively  high  one. 
This  is  further  confirmation  of  what  has  already  been  found  for  this 


COUBSE    OF   PSYCHOPHYSIOLOGICAL    EFFICIEXCY  37 

period.  A  trained  'observer'  for  Giinn,  Kichards  &  Co.,  of  New 
York  City — their  business  is  to  introduce  into  factories  new  systems 
of  shop  management  and  production,  and  in  the  establishing  of  '  unit 
times'  for  the  separate  operations  involved  in  the  making  of  many 
different  articles  they  have  made  thousands  of  observations^  on 
the  speed  of  work— says  this  morning  inefficiency,  also  noted  by  him- 
self, is  'due  to  the  absence  of  the  foreman.'  But  in  the  present 
instances  this  condition  never  occurred  and  could  not  at  all  be  the 
true  reason.  In  addition,  piece-workers  would  be  supposed  to  have 
the  same  prime  incentive  to  maximum  activity  present  at  this  as  at 
any  other  period  of  the  day. 

At  the  12 :30,  5  :30  and  9  :30  periods  several  factors  figure  very 
effectively.  Here  the  most  pronounced  fatigue  tends  to  be  offset 
by  what  has  been  termed  'end-glow' — the  strenuous  attempt  to  in- 
crease the  output  to  the  utmost  limit  at  the  last  moment.  These 
features  are  so  characteristic  that  no  correct  interpretation  of  the 
curves  is  possible  without  their  consideration.  The  periods  imme- 
diately succeeding  those  named  are  influenced  not  only  by  rest  and 
food,  but  also  by  the  social  intercourse  which  has  intervened  since 
the  last  work  period.  Reference  is  again  made  to  Part  D,  where 
general  treatment  of  these  factors  is  preferably  taken  up. 

With  these  things  in  mind,  and  due  reference  to  age  and  pay- 
basis,  some  definite  conclusions  can  be  formulated  from  the  indi- 
vidual records. 

First,  piece-workers  tend  to  follow  the  end-glow  type  and  time- 
workers  the  fag-end  type.  In  group  I.,  of  the  24  cases  at  the  three 
periods  mentioned,  15  show  the  typical  trait,  whence  it  is  safe  to 
judge  that  at  least  half  the  rest  are  affected  by  it,  to  a  lesser  degree. 
Of  the  16  cases  in  group  II.,  7  are  of  this  type  and  6  of  them  were 
directly  due  to  piece-work.*  And  even  the  exceptional  case  of  sub- 
ject 1  is  fully  accounted  for  by  the  fact  that  she  usually  set  4,000 
as  the  limit  for  the  day's  work  and  was  able  to  reach  this  without 
special  effort,  thus  becoming  really  a  time-worker.  Of  the  12  cases 
in  group  III.,  5  follow  the  type  in  question,  1  of  whom  was  a  piece- 
worker. The  influence  of  my  presence  would  be  more  apparent  in 
this  group  and  would  naturally  be  more  pronounced  at  these  than 
at  other  periods,  since  few  can  refrain  from  endeavor  to  'put  the 

^  The  best  stop-watch  (also  time-book)  for  all  classes  of  observational 
work,  of  which  the  author  is  aware,  is  one  designed  for  this  purpose  by  S.  E. 
Thompson,  C.E.,  West  Xewton,  Mass. 

2  It  should  be  noted  here  that  the  period  prior  to  each  of  the  three  in  ques- 
tion may  also  be  affected,  because  the  arbitrary  limitation  of  the  periods  allows 
only  25  or  30  minutes  to  each  of  these  three. 


38  DIURNAL    COURSE    OF   EFFICIENCY 

best  foot  forward' ;  and  in  morning  than  in  afternoon,  of  the  one  day. 
Personal  knowledge  of  the  w'orkers  suggests  that  at  least  five  of  the 
nine  failures  in  the  first  group  to  follow  the  prevailing  type  were  due 
to  physical  inability  to  maintain  the  requisite  pace.  Subject  7,  who 
was  sick  four  days,  could  not  work  up  to  5 :30  and  9  :30  climaxes,  after 
showing  a  decisive  tendency  to  end-glow  at  the  12  :30  period.  Sub- 
ject 8  was  youngest  and  most  inexperienced  and  on  both  accounts 
was  unprepared  to  meet  the  physical  strain  necessary  to  make  these 
special  bursts  of  speed.  For  the  same  reasons,  these  two  subjects 
fail  to  make  a  night  gain  where  the  other  six  do.  As  to  the  time- 
workers,  the  evidence  seems  as  conclusive.  The  last  six  subjects  of 
group  II.  were  paid  by  the  thousand  for  two  days,  and  the  records 
made  then  tend  to  overbear  those  of  the  other  days.  In  but  1  of 
the  16  cases  did  there  seem  to  be  a  naturally  strong  wind-up.  The 
cases  in  group  III.  can  not  be  said  to  alter  these  conclusions  ma- 
terially, as  they  have  not  the  same  weight  even  if  they  evinced  con- 
trary results. 

Second,  it  seems  reasonable  to  believe  that  endurance  as  de- 
pendent on  maturity  is  much  involved.  In  fact,  it  is  impossible  to 
say  how  much  the  falling  off  in  the  production  of  the  time-workers 
at  the  stated  periods  is  to  be  accounted  for  on  the  ground  of  indul- 
gence of  the  feelings  of  fatigue,  due  to  lack  of  the  same  incentive  to 
high  activity  that  piece-workers  possess,  and  how  much  is  to  be  al- 
lowed for  the  fact  of  physical  inability  d~ue  to  immaturity  and  con- 
sequent real  fatigue.  To  the  author,  the  results  for  group  I.  seem 
due  to  the  basis  of  pay  in  its  stimulative  aspect,  while  for  group  II. 
they  seem  considerably  due  to  immaturity,  save  in  the  first  two 
cases.  It  is  not  unworthy  of  note,  in  this  connection,  that  of  the 
five  cases  of  this  group  mentioned  above  as  showing  high  efficiency 
in  the  early  part  of  the  day,  three  are  the  youngest  of  the  eight,  all  of 
whom  have  proportionately  higher  records  at  this  time  of  day  than 
do  the  adults.  Their  curve  as  a  whole  follows  quite  closely  that 
found  by  Christopher  for  the  Chicago  school  children,  seen  in  Fig, 
2  above. 

Neither  piece-  nor  time-workers  can  be  thought  to  exhibit  what 
w'ould  be  the  curve  of  earnest,  ordinary  w'ork;  but  the  former  con- 
ceivably resemble  the  top  extreme  of  such  a  group,  where  the  maxi- 
mum product  is  reached,  while  the  latter  would  represent  the  bottom 
extreme,  where  exists  a  minimum  of  accomplishment  and  a  maxi- 
mum of  yielding  to  the  feelings  of  fatigue.  It  would  scarcely  be 
worth  while  to  carry  the  analogy  to  the  extent  of  determining  the 
theoretical  median  or  modal  curve  of  such  a  group,  to  express  its 
general  tendency.     Likewise,  it  is  scarcely  worth  while  to  seek  gen- 


COURSE    OF    PSYCHOPHYSIOLOGICAL    EFFICIENCY  39 

eral  'type'  curves  of  ability.  That  is,  there  is  danger  in  the  smooth- 
ing-out  process  which  leaves  to  curves  only  their  coarsest  changes. 
It  is  the  positive  tendency  of  all  present-day  scientific  methods  of 
gathering,  registering  and  measuring  data  to  subdivide  phenomena 
more  and  more  in  order  to  get  a  more  accurate  judgment  of  the 
whole  fact  in  the  light  furnished  by  the  more  detailed  and  exact 
definitions  of  the  separate  parts.  This  is  quite  a  contrary  operation 
throughout  to  the  process  of  smoothing. 

This  danger  can  be  thus  illustrated:  an  increase  of  20  per  cent. 
in  efficiency  at  a  certain  hour  may  be  entirely  due  to  a  waking  nap 
in  the  preceding  hour,  where  a  loss  of  only  five  per  cent,  was  sus- 
tained by  reason  of  the  doziness.  We  should  likely  call  the  first  men- 
tioned change  worthy  of  notice  and  the  other  not,  if  smoothing  were 
in  mind,  yet  in  reality  the  one  could  not  occur  without  the  other  and 
indeed  the  results  might,  in  its  absence,  be  just  the  reverse.  This  is 
not  purely  hypothetical,  since  in  Toay  own  case  a  partial  loss  of  con- 
sciousness for  five  minutes  in  the  afternoon  frequently  has  a  very 
appreciable  mental  effect  for  the  better,  though  a  long  and  real  nap 
has  the  opposite  effect. 

There  is  some  satisfaction  and  there  may  be  some  practical  ad- 
vantage in  having  such  gross  'types'  of  endurance,  etc.,  but  they 
hold  the  same  doubtful  position  as  to  actual  explanatory  desiderata 
that  all  other  generalities  occupy.  It  probably  will  be  agreed  that 
this  table  does  emphasize  the  two  types  described,  but  it  is  easy  to 
find  deviations  in  the  individual  curves.  Others  than  these  two  are 
hard  to  locate  and  depict.  Kraepelin  describes  five  or  six  fatigue 
'types',  but  is  enabled  to  do  so  merely  by  grace  of  having  used  but 
four  hours  a  day  in  his  tests :  the  curves  become  more  than  propor- 
tionately complex  when  twice  or  thrice  that  length  of  time  is  utilized, 
and  the  number  of  individuals  falling  under  each  is  correspondingly 
reduced. 

Attention  has  already  been  called  to  the  early  inefficiency  in 
group  I. ;  it  is  now  directed  to  the  more  notable  fact  that  the  highest 
point  is  reached  at  night  by  six  out  of  the  eight.  That  this  would 
remain  as  the  normal  condition  in  regularly  continued  labor  is  not 
likely  (each  was  allowed  to  work  only  eveiy  other  night  during  the 
two  weeks'  continuance  of  the  job).  AYhile  the  results  will,  there- 
fore, not  permit  the  temporal  fixing  of  maximum  performance,  they 
do  serve  to  introduce  a  point  of  considerable  practical  and  psycho- 
logical interest.  That  it  was  possible,  after  a  full  day  of  severe 
effort,  to  increase  the  output  so  notably  and  so  long  suggests  how 
nicely  the  organism  comes  to  be  adjusted  to  the  drains  likely  to  be 


40  DIURNAL    COURSE    OF   EFFICIENCY 

made  upon  it.  It  might  be  truer  to  say  that  there  is  in  the  early 
part  of  a  long  day's  work  an  organic  or  at  least  involuntary  check- 
ing of  the  tendency  to  overdraw  the  store  of  available  energy.  Any- 
way, we  seem  never  to  reach  the  absolute  maximum  of  exertion  pos- 
sible to  us.  Not  only  end-glow,  but  a  number  of  other  things,  espe- 
cially in  the  second  group,  caused  marked  increase  of  ability.  It  is 
worth  knowing  whether  such  induced  bursts  as  the  latter  are  clear 
gains  or  are  counteracted  by  subsequent  inefficiency.  The  solution 
of  this  question  does  not  appear  from  our  data,  because  of  the  many 
unexcluded  factors. 

The  wire-stitching  done  by  the  first  group  does  not  require  any 
special  accuracy  of  movement,  but  decidedly  involves  speed.  Here, 
again,  is  suggested,  as  in  connection  with  the  tapping  tests,  the  possi- 
bility of  nervousness  increasing  the  rapidity  of  certain  sorts  of 
movement  that  do  not  require  precise  muscular  coordinations. 
Women  presumably  are  more  'nervous'  than  men,  and  hence  it  be- 
comes inconceivable  from  the  physiological  standpoint  that  these 
could  have  worked  all  day  near  their  speed  limit  and  not  have  been 
neurally  disorganized  at  the  end.  Their  period  of  greatest  speed 
of  work  thus  coincided  with  their  probable  period  of  greatest 
nervousness. 

3.  Brief  Summary. — The  necessity  is  shown  of  keeping  separate 
the  rate,  accuracy  and  strength  of  movement  and  not  lumping  every- 
thing as  merely  'physical  ability',  while  the  further  division  of  the 
first  two  for  different  types  of  simple  and  complex  movement  is 
strongly  suggested.  Just  what  diurnal  schedule  each  of  these  fol- 
lows has  not  been  fully  demonstrated,  but  some  points  have  been 
definitely  fixed.  As  to  strength  (not  meaning  endurance),  there  is 
ample  reason  for  believing  that  most  commonly  the  first  morning 
power  is  relatively  low,  but  subject  to  a  fairly  rapid  rise  till  about 
11  A.M.,  when  there  is  manifested  a  slight  backward  tendency  till 
1  P.M.  (±:  1  hour),  then  a  gradual  ascent  to  the  maximum  between 
3:30  and  5:30,  whence  there  is  a  much  more  gradual  descent  till 
bed-time,  when  a  second  minimal  point  is  reached — with  adult  males. 
Females  tend  to  push  this  curve  back  at  every  point,  and  children 
still  farther,  apparently  due  to  their  greater  liability  to  physical 
exhaustion;  men  have  more  strength  and  are  less  likely  to  use  it. 
As  to  rate  and  accuracy  of  movement,  there  is  still  found  the  defi- 
ciency at  the  extremes  of  the  day,  but  with  a  marked  tendency  to 
more  accuracy  efficiency  toward  the  morning  end  and  rate  efficiency 
toward  the  night  end,  and  these  tendencies  are  accentuated  as  the 
test  for  accuracy  is  more  complex  and  that  for  rate  more  simple. 
Strength  and  speed  may  be  increased  by  a  highly  nervous  state,  but 


COURSE    OF    PSYCHOPHYSIOLOGICAL    EFFICIENCY  41 

accuracy  is  oppositely  affected.  Female  shop  operatives,  in  addi- 
tion to  confirming  some  of  the  preceding  points,  tend  as  piece-workers 
to  the  end-glow  type  when  approaching  intermissions,  and  as  time- 
workers  and  children  to  the  opposite  extreme,  while  both  classes 
manifest  ability  to  increase  their  product  considerably,  under  special 
stimulation,  at  any  portion  of  the  day  and  despite  the  fact  of  pre- 
vious hard  work. 


C.     COURSE    OF    MENTAL    EFFICIENCY 
I.    The  Simpler  Mental  Activities 

This  field,  having  so  much  in  common  with  the  last,  has  its 
peculiarities,  nevertheless,  which  serve  to  introduce  the  marked  diffi- 
culties characterizing  the  study  of  psychic  life.  It  was  not  because 
the  ancients  found  the  latter  too  easy  a  problem  to  be  worthy  of 
notice  that  scientific  attention  was  turned  outwards,  but  rather  be- 
cause it  was  so  fine-spun  and  intangible  as  to  escape  much  notice. 
The  'popular  mind'  is  yet  quite  free  from  introspective  questionings, 
and  any  such  ignorance  of  the  presence  of  a  problem  is  likely  to  be 
indicative  of  its  difficulty.  Aside  from  any  spiritual  considerations 
which  might  lead  to  the  study  of  psychology  as  the  science  of  the 
soul,  there  is  every  reason  to  believe  that  the  mind's  more  imme- 
diately utilitarian  use  as  a  tool  or  means  for  meeting  the  various 
needs  of  the  higher  life  in  general — volitional,  cognitive,  esthetic,  or 
whatever  one  may  call  them— will  increasingly  force  itself  to  the 
front  in  one  aspect  or  another.  When  it  comes  to  determining  the 
efficiency  of  this  tool  at  different  periods  of  the  day,  for  the  ends 
mentioned,  the  more  radical  complications  of  the  problem  emerge 
into  view.  It  might  be  said  that  the  last  section  had,  on  its  mental 
side,  most  to  do  with  volition;  that  the  present  would  likely  deal 
mostly  with  cognition;  and  the  next,  involving  feelings  of  fatigue, 
etc.,  would  touch  upon  emotion.  With  finer  psychological  analysis, 
it  is  seen  that  this  program,  even  if  fully  realized  experimentally, 
would  still  cover  the  field  only  in  the  grossest  sense. 

1.    Attention 

The  tests  of  the  fluctuation  of  attention,  that  Wiersma^  first  used 
and  Pillsbury-  repeated,  seem  rather  tests  of  the  senses  employed 
than  of  attention  itself.  For  instance,  a  certain  weight  was  placed 
on  a  cork  disk,  of  the  same  size,  on  the  back  of  the  hand,  and  the  just 
perceptibly  different  weight  was  then  determined,  as  also  the  one  dis- 
tinguished with  certainty.  Between  these  two  limits  six  weights  of 
equal  degrees  of  difference  were  used,  the  test  of  attention  being  the 
length  of  time  that  each  of  these  could  be  distinguished  from  the 

^ '  Untersucliungen  iiber  die  sogen.  Aufmerksamkeitsscliwankungen,'  Zeit- 
schrift  fur  Psych,  u.  Physiol,  pp.  179-198.     1902. 

*' Attention  Waves  and  Fatigue.'  Am.  Jour,  of  Psych.,  14:   314.      1903. 

42 


COURSE    OF    MENTAL    EFFICIENCY 


43 


first  as  standard.  For  light  and  sound  stimuli,  six  shades  of  gray 
and  six  gradations  of  sound  were  determined  by  the  same  principle 
as  for  pressure.  Why  it  might  not  be  a  fatigue  coefficient  that  is 
here  obtained,  where  the  senses  are  thus  exercised,  is  not  clear. 
Wiersma's  tests  covered  three  days  with  each  subject.  Pillsbury 
used  only  the  grays  in  his  repetition  of  the  experiment.  Table  XIV. 
gives  the  results  of  both  authors. 

Table   XIV.    Attention — per   different    senses — Wiersma,   Pillsbury. 


Subject. 

Test. 

Morning. 

Noon. 

Afternoon. 

Night. 

Wiersma. 

Time.     M.V. 

Time.     M.V. 

Time.     M.V. 

Time.     M.V. 

H 

Pressure. 

204.6     10.9 

239.5 

8.9 

161.9     14.1 

W 

a 

201.0      6.1 

251.1 

3.0 

283.5       1.7 

11 

Light. 

180.0        — 

228.4 

— 

255.8        — 

II 

Sound. 

217.2        — 

235.4 

-  — 

256.1        — 

Male  nurse. 

u 

217.2      5.8 

209.2 

6.2 

216.0      5.3 

Female  nurse. 

(( 

241.6       1.7 

248.0 

1.8 

242.0      4.6 

Female  nurse. 

u 

202.2      4.8 

215.0 

4.4 

197.0      3.6 

Pillsbury. 

No.     VII   Sum. 

No. 

VII    Sum. 

No.     VII 

Sum. 

No.      VII    Sum. 

P 

Light. 

300    2.4    9.6 

245 

2.5     8.5 

337   2.6 

8.2 

365  1.6     7.5 

H 

(( 

287    3.4    9.4 

230 

2.6    8.7 

285   3.3 

9.3 

300  2.9    9.0 

G 

ti 

249    1.2    8.9 

181 

1.3    8.9 

265    1.2 

8.4 

377  1.2    8.4 

W 

(( 

275    1.5    5.4 

196 

1.6    6.3 





281  1.5    5.1 

F 

(( 

73   5.0  18.9 

37 

4.7  18.2 

79    3.4 

13.4 

63  4.5  18.8 

K 

(( 

38    1.6  13.5 

42 

1.9  14.4 

41    3.4 

14.6 

33  5.6  22.0 

No.  =  number  of  waves  measured. 

V/I  =  ratio  of  visible  to  invisible  periods. 

Sum  =  length  of  attention  wave. 


Wiersma  is  uniformly  worst  in  the  morning  and  best  at  night, 
while  H  has  another  order.  It  is  strangely  concluded  that  those  of 
little  mental  training  do  not  show  definite  variations  and  that  these 
are  due  to  general  practise  in  mental  work.  A  tendency  in  students 
to  raise  the  night-end  of  efficiency  may  exist,  but  his  subjects  are 
too  few  and  incomparable,  and  the  results  too  discordant,  to  allow 
such  an  inference. 

Pillsbury  experimented  on  six  subjects  from  one  to  six  days. 
The  first  three  records  are  obviously  more  reliable  than  the  last 
three.  ¥7ith  the  exception  of  K  (Kiilpe),  who  was  a  very  strong 
night-worker,  they  point  to  a  morning  maximum  and  a  night  mini- 
mum in  efficiency  of  attention.  Pillsbury  says  that  Slaughter  and 
Bonser  independently  have  found  the  attention  wave  to  correspond 
to  the  Traube-Hering  wave-length  for  blood  pressure.  This  suggests 
a  correlation  with  the  diurnal  variations  in  pulse  and  respiration 


44 


DIURNAL    COURSE    OF   EFFICIENCY 


rates,  which  Galloway,  in  an  unpublished  investigation,  finds  really 
to  exist. 

It  is  not  easy  to  see  how  fatigue  effects  could  fail  to  operate  in 
such  protracted  experiments  with  senses  where,  according  to  the 
prevailing  idea,  it  is  wont  to  appear  quite  early.  The  main  fact 
measured  would  then  have  been  sensory  more  than  attention al,  as 
intimated  above.  The  difference  of  opinion  may  be  merely  defini- 
tional. 

Lobsien^  refers  to  some  work  by  Schuyten,  of  Antwerp,  on 
changes  of  attention  in  school  children  eight  to  ten  years  old,  carried 
on  for  a  school  year — to  determine  atmospheric  effect.  At  four 
periods  of  the  day  the  number  of  times  in  five  minutes  they  invol- 
untarily raised  their  eyes  from  an  assigned  reading  was  noted.  The 
results  having  a  bearing  here  may  be  briefly  stated  thus :  ' '  The  atten- 
tion of  school  children  diminishes  from  8  :30  to  11  and  again  from 
2  to  4;  is  greater  at  2  p.m.  than  at  11  a.m.,  but  always  less  than  at 
8:30  A.M."  Using  the  same  method,  Lobsien  found  the  following 
results : 

Table  XV.     Variation  of  Attention  of  School  Children — After  Lobsien. 


A.M. 
P.M. 


Jan. 

Feb. 

Mar. 

Apr. 

May. 

June. 

July. 

Aug. 

Sept. 

Oct. 

Nov. 

64 
59 

59 
55 

57 

57 

55 

52 

47 
49 

45 
47 

39 

42 

— 

— 

52 
50 

55 
51 

Dec. 

62 
58 


Numbers  mean  per  cents,  of  pupils  not  raising  the  eyes. 

It  will  be  seen  that  the  morning  or  afternoon  is  the  better  accord- 
ing to  the  time  of  year,  morning  being  more  favored  on  the  whole. 
This  method  seems  better  than  the  preceding,  is  simple  and  easy  of 
application  and  measurement.  The  results  are  more  concordant, 
possibly  due  to  age,  as  well  as  more  reliable. 


2.    Discrimination 

For  testing  discrimination  of  letters,  I  used,  in  most  of  the  series, 
a  printed  form  of  500  capital  letters— 100  A's  and  16  each  of  the 
other  letters  of  the  alphabet  intermixed  in  irregular  order.  By  some 
of  the  subjects,  1  of  these  16  letters  was  marked  out  each  period; 
by  others,  more  than  one.  The  marking  out  was  done  as  rapidly  as 
consistent  with  correctness  and  was  timed  by  a  stop-watch.  The 
most  conspicuous  letters  were  not  used,  and  the  rest  were  so  arranged 
that  each  occurred  once  in  each  period  every  three  days,  thus  weight- 

* '  Schwankungen  der  psyehischen  Kapazitat,'  Pddag.  Psych.,  V.  Bd.,  7 
Heft.      1902. 


COURSE    OF    MENTAL    EFFICIENCY 


45 


ing  each  period  alike  as  to  the  varying  difficulty  of  different  letters. 
The  average  time  and  its  P.E.,  and  the  average  number  of  omissions 
are  shown  for  each  subject  in  the  following  table: 


Table   XVI.     Discrimination   of   Letters — Letter   Blank. 


Subject, 


I.  1  letter 
IL       " 
IIL       " 
V. 

VL       " 

Average 


II  letter 
2  letters 
3      " 
4      " 

Average 


II  letter 
2  letters 
3      " 
4     " 

Average 


IV.  2  letters 


No.  of 


14 
12 
12 
12 
11 

12 


14 
10 
10 

8 

10 


14 

7 
6 
6 


10 


7-9  A.M. 
Time.  P.E.  Omis. 


58.5  0.76  1.2 

63.8  1.11  0.3 

42.0  0.69  0.6 

71.8  1.03  0.8 

42.5  0.43  2.3 

55.7  0.80  1.0 


58.5  0.76  1.2 

84.8  1.00  3.9 

112.2  1.19  5.1 

141.5  1.26  5.9 

99.2  1.05  4.0 


12-2  P.M. 
Time.  P.E.  Omis. 


54.8  0.69  1.3 

60.3  1.23  0.6 

41.0  0.74  0.7 

60.7  0.73  1.3 

41.3  0.70  3.0 

51.6  0.62  1.4 


76.2  2.01  0.9 

97.0  0.88  7.3 

144.2  1.64  5.8 

167.3  2.13  6.9 

121.2  1.64  5.2 


107.7  1.92  2.5 


54.8  0.69  1.3 

76.3  0.91  4.2 
106.0  1.04  5.6 
13L6  1.99  6.4 

92.4  1.16  4.4 


103.0  0.96  2.8 


5-7  P.M. 
Time.  P.E.  Omis. 


54.8  0.57  2.3 

63.4  1.36  0.2 
44.0  0.53  0.7 
63.6  1.21  1.1 

40.5  0.70  2.5 

53.5  0.88  1.4 


54.8  0.57  2.3 
77.1  0.70  5.5 


9-11  P.M. 
Time.  P.E.  Omis. 


59.0  0.62  1.4 

66.1  1.57  0.7 

44.5  0.61  0.9 

70.6  0.68  1.3 

40.2  0.70  2.2 

56.1  0.84  1.3 


59.0  0.62  1.4 
81.6  1.36  4.2 


108.1  1.91  5.6,116.6  2.05  6.1 
132.4  1.25  7.6  140.0  1.63  7.1 

93.1  Lll  5.2    99.3  1.41  4.7 


79.5  1.61  0.9     78.3  1.21  0.6 

95.1  0.83  4.6  107.8  0.93  3.9 

139.3  2.05  8.0  166.9  1.76  3.7 

169.2  2.42  5.6  |182.1  3.12  6.7 

120.8  1.73  4.9  133.8  1.76  3.7 


110.1  1.27  3.4  118.6  1.32  2.9 


The  maximum  ability  is  found  at  noon,  the  minimum  at  the 
extreme  periods.  It  being  winter,  the  tests  at  the  latter  times  were 
often  performed  under  artificial  light,  which  may  account  for  some 
of  the  difference.  The  omissions  seem  to  vary  inversely  as  the  time, 
which  fact  would  also  decrease  the  differences  between  periods,  as 
to  their  total  efficiency.  Subject  A  does  comparatively  better  in 
the  morning  and  decidedly  worst  at  night. 

Group  B  marked  out  two  letters  simultaneously  and  then  a  second 
combination  of  two  on  another  blank,  under  a  constant  time-limit 
of  90  seconds  for  each  period.  The  results  appear  in  the  next  table, 
in  terms  of  the  average  number  of  letters  undone  and  omitted. 


Table    XVII.     Discrimination    of    Letters — Letter    Blank. 


Sub- 
ject. 

No.  of                   9:00  A.M. 
Blanks.  Undone.  P.E.    Omis.  P.E. 

12 :  00  M. 
Undone.  P.E.    Omis.  P.E. 

4 :  00  P.M. 
Undone.  P.E.  Omis.  P.E. 

B 

32        2L2     1.14  12.4  0.72 

26.1     0.98  11.1  0.97 

28.2    1.71    12.3  0.99 

This  shows  a  gradual  increase  of  inefficiency   from  9  a.m.  on. 
The  difference  here  may  be  due  to  sex,  as  subject  A  also  shows  a 
much  worse  night  rate  in  this  than  in  most  of  her  tests.      This  in- 
crease Avas  in  spite  of  practise  effect. 
4 


4G 


DIURNAL    COURSE    OF   EFFICIENCY 


In  a  similar  test,  but  using  a  book,  subject  I.  marked  out  the  e's 
on  a  page;  then,  in  another  series,  the  a's.  The  first  period  and  the 
last  two  were  subject  to  slight  interruption,  but  the  others  to  more. 

Table  XVIII.     Discrimination  of  Letters — Book  Pages. 


3 

1 

7:00  A.M. 
Time.  P.E.  Omis. 

10:00 
Time.  P.E.  Omis. 

12:00-1:00  P.M 
Time.  P.E.  Omis. 

4:00 
Time.  P.E.  Omia. 

I. 
I. 

e 
a 

12 

17 

27.5  .41     .73 
28.5  .32    .37 

26.2  .40     .99 
26.6  .29    .35 

27.2  .23  1.27 
27.1  .37     .41 

25.6  ,19   1.01 

26.7  .34     .60 

Average 

15 

28.0  .36    ,55 

26.4  .35    .67 

26.1  .30     .84 

26.2  .26     .80 

J2 

3 

ll 

7:00  F  M. 
Time.     P.E.     Omis. 

Time. 

10:00 
P.E. 

Omis. 

12:00  M. 
Time.     P.E.     Omis. 

I. 
I, 

e 
a 

12 
17 

26.0      ,20       ,74 
26.5      .35       .45 

28.7 
29.8 

.56 
.37 

1.12 
.21 

30.0      ,23       .73 

Average 

15 

26.3     .28       .59 

29.2 

.46 

.66 

30.0     .23      .73 

No  correction  was  made  in  'time'  for  the  varying  number  of  e's 
to  a  page,  as  the  same  function  is  exercised  in  their  absence  as  in 
their  presence,  but  a  slight  allowance  was  made  in  'omissions.'  The 
order  of  abilities  is  about  that  found  by  the  previous  test,  and  the 
inverse  relation  of  rate  and  accuracy  is  again  hinted  at. 

Among  the  Exposition  tests  was  one  involving  mainly  judgments 
of  shape  and  size,  and  a  motor  element.  In  a  board,  a  foot  square, 
were  cut  nine  shallow  holes  of  various  sizes  and  shapes  and  in  an 
irregular  order.  These  shapes  were  partly  in  pairs,  the  members  of 
which  more  or  less  closely  resembled  each  other — in  order  to  render 
their  discrimination  the  more  difficult.  Blocks,  shaped  like  the 
holes  and  supplied  with  handles,  were  to  be  inserted  by  the  subject 
at  the  maximum  speed  possible  and  with  the  minimum  error.  The 
following  average  record  was  made  by  60  Filipinos  in  the  morning 
and  40  in  the  afternoon:  a.m.,  time,  25.0  seconds,  mistakes,  1.00; 
P,M,,  time,  25,5,  and  mistakes,  0,76,  This  is  but  a  chance  difference, 
if  both  ways  of  scoring  be  taken  into  account. 


3.    Association 

Reaction-time,  naming  colors,  and  Avord  associations  will  be  con- 
sidered in  this  connection.  All  involve  discriminative  and  motor 
elements  in  varying  degrees. 

The  experiments  in  reaction-time  are  limited  in  number.  In 
simple  reactions  to  a  sound-stimulus,  two  subjects  were  tested  with 
the  Hipp  chronoscope  three  times  daily  for  four  days,  five  reactions 
with  each  hand.      In  controlled  reactions,  two  subjects  were  tested 


COURSE    OF    MENTAL    EFFICIENCY 


47 


for  seven  days,  reacting  to  colors  exposed  by  an  electrical  drop- 
screen  in  about  three-thousandths  of  a  second.  The  combinations 
of  colors  in  a  first  series  of  experiments  were  standard  red  and  green, 
red  and  orange ;  in  a  second  series,  red  and  the  same  red  mixed  with 
50  per  cent,  of  orange  (R-0),  then  red  and  red  with  25  per  cent, 
orange  (0-R).^     The  results  of  both  forms  of  tests  are  in  Table  XIX. 


Table  XIX.    Keaction-time  and  Time  of  Day. 


Subject. 

No.  of 
Keactions. 

9 :  00  A.M. 

12:30  P.M. 

5 :  00  P.M. 

Time.  P.E.  1  Time.  P.E. 

Time.  P.E.    Time.  P.E. 

Time.  P.E.  1  Time.  P.E. 

Simple  reaction.        Eight.          Left.          Eight.          Left.          Eight.          Left. 

I.            20 
VII.            20 

162   2.88 
142   3.87 

181    2.99 
133    2.74 

152    2.52 
132    3.21 

149   2.01 
118   3.32 

152   2.93    150   2.71 
129   3.16    124   3.37 

Controlled  reaction.  E.  &  G.     E.  &  O.       E.  &  G.      E.  &  0.       E.  &  G.       E.  &  0. 

I.          208         255    1.51 
III.          208        247    1.51 

281    1.56 
272    1.27 

244    1.62    278   1.56 
246    1.16    264    1.46 

253    1.62 
244    1.11 

283    1.38 
268    1.38 

Controlled  reaction.  E.&E-O.  E.  &0-E.  E.  &  E-0.  E.  &  0-E.  E.  &  E-0.  E.  &  0-E. 

I.          156        265    1.45 
IIL          156        279    1.20 

274   1.26    265    1.39 
285    1.13    271    1.00 

276    1.52 
278    1.13 

266    1.39 
273    1.39 

280  1.26 

281  1.44 

The  superiority  of  the  later  two  periods  is  apparent,  and  it 
should  additionally  be  said  that  on  two  of  the  days  it  was  so  cloudy 
(January)  that  electric  lights  had  to  be  used  a  short  part  of  the  last 
period.  Possibly  the  motor  element  here  has  much  influence  in 
shaping  the  curve. 

Ostanikow  and  Grau'  measured  four  adults  with  the  Hipp  instru- 
ment—themselves, a  servant  (18  years)  and  a  peasant  (65).  The 
periods  were  9  a.m.,  1,  4  and  7  p.m.  They  found  the  simple  reaction- 
time  shortest  in  early  morning  and  the  complex  in  early  evening. 
Divergent  results  would  be  expected  from  so  heterogeneous  an  age 
group. 

Work  done  by  Cattell  and  by  Ellis  and  Shipe  in  connection  with 
fatigue  investigations,  will  be  referred  to  later  (see  p.  82). 

For  the  test  in  naming  colors,  ten  one-cm.  squares  of  each  of  ten 
different  colors  were  pasted  at  intervals  of  one  cm,  on  white  card- 
board, in  irregular  order.  The  subjects  named  these  aloud  as  rapidly 
as  possible,  taking  the  time  with  a  stop-watch.     By  holding  the  card 

^  This  is  also  part  of  an  investigation  by  Dr.  V.  A.  C.  Henmon,  Columbia 
University. 

-  Bechterew,  '  Ueber  die  Geschwindigkeitsveriinderungen,  etc.,'  Neur.  Central- 
llatt.,  12,  9  Bd.     1893. 


48 


DIURNAL    COURSE    OF   EFFICIENCY 


in  different  positions,  the  colors  were  presented  in  four  different 
orders ;  and  the  experiment  was  so  arranged  that  the  same  order  was 
not  presented  in  any  two  consecutive  tests,  though  each  order  was 
used  during  a  whole  series  an  equal  number  of  times  for  each  period 
of  the  day.  In  the  results,  the  first  two  days'  records  were  omitted 
in  allowance  for  practise. 

Table  XX.     Naming  100  Colors. 


Subject. 

7-9  A  M. 

12-2  P.M. 

4-6  P.M. 

9-11  P.M. 

Time. 

P.  E. 

Time 

P.  E. 

Time. 

P.  E. 

Time. 

P.  E 

I. 

1,000 

61.8 

0.76 

56.0 

0.62 

55.2 

0.48 

59.2 

0.51 

II. 

1,000 

68.8 

1.10 

62.1 

0.76 

6.3.1 

0.67 

67.3 

1.22 

V. 

1,000 

59.1 

1.30 

50.9 

0.74 

51.6 

0.73 

55.3 

0.44 

A  . 

1,000 

60.1 

0.91 

— 

— 

57.1 

0.97 

57.8 

1.15 

Here  again  the  motor  element  may  somewhat  account  for  the 
obvious  similarity  to  the  diurnal  curve  already  found  for  speed  of 
movement. 

In  a  lengthy  list  of  tests  given  to  Columbia  students  in  their 
entering  and  final  years,  this  one  shows  in  the  results  a  decided  im- 
provement to  have  occurred  in  the  interval.  This  may  be  cor- 
related with  the  intellectual  development  which  has  presumably 
taken  place,  but  may  on  the  other  hand  be  correlated  with  the  phys- 
ical growth  that  has  intervened.  This  test  is  not  so  simple  as  it 
seems.  Among  the  perceptional,  associational,  expressional  and 
other  factors,  one  can  not  say  how  the  time  should  be  distributed, 
and  yet  just  such  knowledge  as  this  in  all  our  tests  is  required  to 
properly  relate  the  results  obtained.  The  progress  made  in  this 
refined  work  of  correlating  different  functions  with  reference  to  their 
common  or  dissimilar  elements  will  largely  determine  the  value  of 
the  experimental  psychology  of  coming  years,  from  both  the  scien- 
tific and  the  pedagogical  points  of  view. 

In  'simple'  word  associations,  at  each  period  a  list  was  used  of 
16  words  (4  nouns,  4  adjectives,  4  verbs,  4  adverbs  and  prepositions), 
selected  at  random  but  arranged  in  a  definite  order.  After  each 
word  was  to  be  written  the  first  one  occurring  to  the  mind  after 
seeing  it.  Time  w^as  taken  as  in  the  other  tests.  The  lowest  section 
of  Table  XXI.  gives  results. 

For  controlled  word  associations,  420  words  were  selected,  as 
nearly  equal  in  difficulty  as  possible.  From  these,  random  lists  of 
ten  words  each^  M^ere  made  up  and  these  given  to  the  subjects.  It 
was  hoped  by  a  random  arrangement  to  obviate  differences  of  diffi- 

^  As  '  .supple,  terse,  aroused,  insipid,  ulterior,  negligent,  fitful,  courage,  pro- 
fuse, stately.' 


COURSE    OF    MENTAL    EFFICIENCY 


49 


culty  in  the  words.  A  word  of  opposite  meaning  was  to  be  written 
after  each  one  on  the  list.  Words  were  chosen  whose  opposites  could 
not  be  (easily)  formed  by  annexation  of  prefixes  or  suffixes  of  nega- 
tion, or  by  omission  of  the  same.  Of  course  it  was  impossible  to 
avoid  this  entirely,  though  the  subjects  were  also  instructed  not  to 
make  use  of  such  opposites.  Those  taking  the  test  thus  are  reported 
in  the  first  section  of  Table  XXI.  The  middle  section  gives  the 
resulting  figures  when  A  and  I.  used  two  of  the  lists  at  a  period,  the 
rate  for  each  list  being  shown  in  the  case  of  A. 


Tabije  XXI.     WoED  AssociATioxs — Simple  and  Controlled. 


Subject. 


No.  of  7-9  A.M.  12-2  P.M.  4-6  P.M.  9-11  P.M. 

Words.  Time.     P.E.     Mis.  Time.      P.E.     Mis.  Time.     P.E.     Mis.  Time.      P.E.     Mis. 


Controlled  — 10  Opposites. 


I. 

100 

II. 

100 

III. 

100 

IV. 

100 

V. 

100 

Average 

100 

A. 

140 

69.7 
50.6 
48.4 
76.0 
54.2 


2.72 
1.72 
1.27 
2.74 
2.23 


0.5 
0.1 
0.1 
0.6 
1.9 


59.8     2.14    0.6 
63.8    3.01     0.1 


60.1 
43.6 
41.4 

74.8 
46.6 


1.23 
1.71 
0.94 
2.83 
1.64 


0.4 
0.1 
0.2 
1.1 
1.9 


53.5    1.67    0.7 


59.3 
46.0 
44.0 

70.7 

48.2 

53.6 

57.2 


2.46 
1.76 
1.36 
2.95 
1.19 

1.94 

2.07 


0.4 
0.0 
0.3 

0.8 
1.4 

0.6 
0.1 


70.3 
45.1 
45.0 
71.2 
45.0 

55.5 
61.2 


2.32 
2.36 
1.68 
2.30 
0.96 

1.92 

2.86 


0.3 
0.1 
0.1 
0.4 
0.5 

0.5 
0.2 


Controlled 

—  20  Opposites. 

I.  per  10 
A.  1st  10 
A.  2d  10 

100 
70 
70 

56.2    2.12    0.2 
46.0    2.91     0.2 
50.4    3.00    0.3 

55.8 

1.74    0.6   55.5    1.97     1.0 
38.7    1.91     0.1 
39.4    2.13    0.1 

57.5     1.86    0.5 
47.7    2.33    0.1 
45.0    2.97    0.2 

Simple  — 16  Words. 


160 
162 


51.8    0.51 
51.0    0.83 


51.4    0.58 


49.9 
53.8 


0.50 
0.92 


50.2    0.59 
53.9    1.10 


This  table  makes  the  first  period  of  the  day  the  worst,  while  noon 
seems  the  best.  The  P.E.'s  show  that  a  longer  series  is  needed,  but 
it  would  be  exceedingly  difficult  to  find  in  the  150,000  usable  words 
of  the  English  language  100  more  with  the  requisite  qualifications 
for  this  test. 

Fifty  of  these  words  were  given  to  the  group  of  young  women, 
240  seconds  being  allowed  in  which  to  write  the  opposites.  To  bring 
this  more  into  line  with  the  others,  the  number  of  words  undone  was 
used  as  the  basis  of  the  estimates.  The  results  were :  9  a.m.,  undone 
19.1  and  mistakes  3.5 ;  12  m.,  18.3  and  2.3  ;  4  p.m.,  17.0  and  3.4.  The 
difterences  here  are  not  decisive:  the  P.E.'s  are  large,  because  the 
subjects  hunted  easy  words  instead  of  taking  them  seriatim.  The 
morning  figures  are  probably  affected  by  newness  of  test. 

This  test  seems  of  doubtful  utility  for  the  present  purpose,  if  it 
is  admitted  that  w^riting  ability  varies  for  time  of  day.      Subjects 


50 


DIURNAL    COURSE    OF   EFFICIENCY 


I.,  IV.,  v.,  A  and  B  took  the  rate  test  for  writing  and  the  general 
order  of  each  in  the  two  cases  is  notably  similar  (see  Table  IV.,  p. 
18).  The  qnicker  the  real  association-time  of  the  individual,  the 
greater  would  such  vitiation  be.  Being  designed  for  the  use  of  stu- 
dents, the  words  picked  were  of  two  and  three  syllables,  with  some 
hard  monosyllabics  needed  to  fill  out  the  desired  number.  This 
meant  long  opposites,  and  much  time  devoted  to  the  merely  mechan- 
ical act  of  writing.  Also,  while  100  words  at  each  period  give  fair 
chance  for  equal  distribution  of  hard  ones,  the  P.E.  in  this  test  will 
always  remain  large  on  account  of  them.  The  inverse  relation  of 
speed  and  mistakes,  seen  in  the  results,  again  shows  the  need  of  a 
coefficient  which  would  allow  the  transmuting  of  the  one  into  terms 
of  the  other,  and  it  is  not  altogether  improbable  that  such  a  figure 
could  be  found  if  careful  search  w^ere  made. 

4.    Memory 

This  was  tested  in  several  ways.  Subject  I.  selected  1,200  Ger- 
man words,  with  which  he  was  unfamiliar,  and  arranged  them  in 
random  lists  of  ten  each,  with  their  corresponding  English  meanings. 
The  time  consumed  in  memorizing  one  of  these  lists,  maintaining 
correctness  of  meanings  and  relative  positions  of  all  words,  was  se- 
cured at  ten  periods,  for  twelve  days.  The  lists  were  used  a  full 
year  after  their  preparation.  The  external  conditions  during  the 
progress  of  this  test  were  excellent,  being  practically  unvaried  from 
day  to  day.  The  entire  twelve  days  were  devoted  to  experimenta- 
tion, from  7 :30  a.m.  till  11  p.m.,  excepting  for  meals,  8  to  8 :30 
A.M.,  12  to  1 :30  P.M.,  6 :30  to  7  :30  p.m.  The  same  thing  was  done  at 
the  same  hour  each  day.  This  program  was  adhered  to  without 
change  and  without  interruptions,  so  that  none  but  constant  causes 
influenced  any  of  the  trials.  But  the  increasing  monotony  of  the 
task  may  have  somewhat  afi'ected  the  later  periods  of  the  last  few 
days.  The  results,  in  Table  XXII.,  are  in  terms  of  the  average  num- 
ber of  seconds  required  to  learn  each  list  fully. 

Table  XXII.    Memory — 10  German  Words  and  Their  Meanings. 


No.  of 
Words. 


120 


7  A.M. 
Time.     P.E. 


371  10.26 


8:30 
Time.     P.E. 


390  14.34 


10:00 
Time.     P.E. 


386   10.09 


11:30 
Time.     P.E. 


434  16.89 


1:80  P.M 
Time.     P.E. 


475    12.11 


3:00 
Time     P.E. 


460    11.21 


No.  of 
Words. 


120 


4:30 
Time.     P.E. 


445    15.19 


6:00 
Time.     P.E. 


431    15.02 


7:30 
Time.     P.E. 


444   16.72 


9:00 
Time.     P.E. 


544   15.13 


10:30 
Time.     P  E. 


613   17.33 


This  table  shows  some  clear  variations.      The  morning  is  by  far 
the  best;  a  slump  occurs  between  1  p.m.  and  3:30  p.m.;  then  a  level 


COURSE    OF    MENTAL    EFFICIENCY 


51 


period  till  8  p.m.;  after  which  there  is  a  decided  drop.  The  normal 
curve  of  the  author's  subjective  feelings  follows  a  like  course,  save 
as  to  the  degree  of  the  night  drop.  The  other  tests  of  memory  on 
myself  should  not  have  the  same  weight  as  these  figures,  though,  as 
a  matter  of  fact,  they  corroborate  them. 

This  subject  used  also  lists  of  eight  single  numerals  for  visual 
memory,  exposing  at  a  uniform  rate  the  successive  figures  on  cards. 
Three  of  these  were  used  each  period  for  thirty  days.  The  first 
period  and  the  last  two  were  liable  to  little  interruption;  the  others 
to  more.  Only  the  average  number  of  mistakes  is  shown  in  the 
following  results : 

7  A.M.,  0.8  ;  10  A.M.,  1.9  ;  1  P.M.,  1.8  ;  4  P.M.,  1.8  ;  7  P.M.,  1.5  ;  10  P.M.,  1.2. 

The  middle  three  can  not  be  compared  with  the  others,  for  the 
reason  already  stated,  but  show^  no  differences  among  themselves. 
The  first  period  is  most  probably  the  best. 

Subjects  III.,  IV.,  V.  and  VI.  pursued  the  same  method  with  lists 
of  nine  figures.  They  counted  their  own  mistakes,  cases  of  incorrect 
order  being  called  erroneous  as  well  as  wrong  figures.  The  P.E.'s 
are  calculated  from  the  whole  series,  though  some  practise  effect  is 
apparent— but  two  days  w^ere  omitted  for  III.  The  results  are  the 
first  in  Table  XXIII. 


Table  XXIII.    ^MEitoRY — 9  FiorRES  xyo  16  Words. 


Figures. 

No.  of 

Lists. 

7-9  A.M. 
Misses.    P.E 

12-2  P.M. 
Misses.    P.E. 

5-7  P.M. 
Misses.    P.E. 

9-11 
Misses 

P.M. 

Subject. 

P.E. 

III. 

IV. 

V. 

VI. 

Average 

30 
30 
36 
30 

32 

1.5 
3.1 
5.8 
3.3 

3.4 

0.38 
0.53 
0.37 
0.40 

0.42 

1.2 
2.6 
4.0 
3.1 

2.7 

0.39 
0.32 
0.42 
0.34 

0.37 

1.1 
3.1 
3.3 
2.0 

2.4 

0.26 
0.33 
0.54 

0.48 

0.40 

1.8 
3.4 
4.7 
3.9 

3.4 

0.27 
0.34 
0.47 
0.39 

0.37 

Words. 

! 

I. 
II. 
A 

48 
48 
48 

8.1 
4.0 
6.2 

0.58 
0.23 
0.28 

10.4 
9.0 

1.71 
0.44 

9.4 
6.1 
6.1 

0.82 
1.10 
0.29 

9.8 
7.2 
7.1 

0.91 
0.55 
0.31 

Figures. 

<  Visual 

^-  Auditory... 
^  Vis.-Aud... 

Average 

24 
42 

16 

27 

1.5 
1.3 

1.0 

1.3 

0.18 
0.31 
0.32 

0.27 

2.5 
0.7 
1.3 

1.5 

0.39 
0.18 
0.28 

0.28 

3.1 
2.2 
1.3 

2.2 

0.76 
0.52 
0.35 

0.54 

Subjects  I.,  II.  and  A  were  tested  in  visual  memorj^  with  words 
—  four  groups  of  four  words  each,  every  period.  The  words  of  a 
group  were  more  or  less  logically  connected,  as  they  were  cut  from 
newspaper  sentences.      These  partial  clauses  had  been  pasted  on 


52  DIURNAL    COURSE    OF   EFFICIENCY 

separate  strips  of  cardboard,  for  ready  exposure,  as  in  the  other 
memory  test.  Hence  each  effort  of  the  memory  was  an  attempt  to 
recall  sixteen  words  thus  arranged  and  handled.  The  results  in  the 
middle  section  of  Table  XXIII.  are  in  terms  of  the  mistakes. 

For  subject  A,  results  from  the  following  tests  are  then  shown: 
(1)  visual  memory,  with  lists  of  nine  figures;  (2)  auditory,  similar 
lists  being  read  aloud  to  the  subject;  (3)  auditory-visual,  the  figures 
being  both  heard  and  seen  simultaneously. 

The  first  group,  consisting  of  the  four  subjects  III.,  IV.,  V.,  VI., 
as  a  whole  conforms  the  most  closely  to  the  type  of  efficiency  reach- 
ing a  significant  maximum  in  the  midday  periods.  But  in  the  other 
subjects  the  tendency  is  strong  to  a  morning  maximum  and  to  a  noon 
minimum,  in  the  ease  of  the  males,  and  a  night  minimum  for  the 
females. 

The  auditory  memory  tests  with  numerals  were  given  to  the 
Teachers  College  female  students,  six  lists  being  used  at  each  period 
for  one  day ;  and  to  subject  VII.,  three  lists  being  used  at  each  period 
for  four  days.     Results : 


Mis. 

B. 

P.  E. 

Mis. 

VII. 

P.  E. 

9    A.M.,             ' 

9.0 

0.7 

4.5 

0.6 

12  M.,              1 

6.9 

0.6 

4.5 

0.8 

4   P.M.,              I 

7.0 

0.5 

4.8 

0.5 

Newness  of  the  test  at  the  first  period  and  practise  effect  at  the 
others  tend  to  make  these  differences  problematical  in  the  case  of  the 
young  women,  while  they  seem  chance  differences  in  case  of  sub- 
ject VII. 

Larguier^  memorized  passages  of  ten  sentences  from  Racine  and 
measured  results  in  number  of  seconds  required  to  do  the  learning, 
obtaining,  before  coffee,  316  (av.  of  16  days)  ;  before  lunch,  349  (8 
days)  ;  after  lunch,  341  (7  days)  ;  before  dinner,  345  (9  days)  ;  after 
dinner,  280  (5  days).  In  reproduction  of  the  passages  24  hours 
later,  he  found  the  best  results  after  dinner  and  the  worst  at  the 
first  period.  Besides  being  the  record  of  only  one  subject  these  re- 
sults fall  under  the  criticism  explained  early  in  this  paper  (p.  2),  in 
that,  as  seen  from  the  differing  figures  in  parentheses,  valid  results 
were  expected,  in  short  series,  from  experiments  where  every  period 
of  the  maximum  number  of  days  reported  had  not  been  duly  used.^ 

^ '  Note  sur  les  Variations  de  la  Memoire  au  Cours  de  la  Journee,'  L'Ann4e 
Psych.,  8:  205-213.     1901. 

^This  is  strikingly  shown  in  another  series,  of  ostensibly  14  days'  length, 
testing  the  effect  of  alcohol  on  memory,  where  only  rarely  do  two  experiments 
seem  to  have  been  taken  the  same  day  before  and  after  lunch. 


COURSE    OF    MENTAL    EFFICIENCY  53 

Thus  no  account  was  taken  of  the  inevitable  difference  of  efficiency 
between  one  day  and  another. 

M.  C.  Schuytens,  in  an  article  soon  to  be  mentioned,  finds  memory 
in  school  children,  in  class  tests,  to  be  dependent  on  whether  their 
first  trials  are  made  in  the  morning  or  in  the  afternoon.  In  other 
words,  it  is  entirely  a  matter  of  interest  with  them :  they  lose  interest 
after  the  first  trial. 

The  total  outcome  as  to  memory  must  be  considered  a  negation 
of  the  existence  of  a  simple  diurnal  memory  curve,  though  this  point 
will  be  touched  again  in  the  subsequent  discussion  of  fatigue. 


II.    The  IMoRE  Complex  IMental  Activities 
1.    Arithmetic 

This  has  long  been  a  favorite  test,  supposedly  of  general  mental 
efficiency.  This  special  preference  has  been  due  largely  to  the  tradi- 
tional conception  that  no  other  school  branch  is  so  difficult  for  the 
ordinary  student  to  master,  that  it  is  more  purely  logical  in  nature, 
and  partly  to  the  experimental  evidence  furnished  by  certain  in- 
vestigators of  the  question  of  school  fatigue. 

It  is  scarcely  allowable  at  the  present  day  to  accept  an  arith- 
metical test  as  a  measure  of  general  mental  efficiency.  The  mere 
fact  of  difficulty  does  not  prove  it  to  be  such  a  measure ;  rather  must 
the  causes  of  this  difficulty  first  be  determined  by  means  of  refined 
empirical  analysis,  which  can  not  be  attempted  here.  An  arith- 
metical test  does  no  doubt  call  for  the  exercise  of  various  important 
mental  powers,  such  as  attention,  discrimination,  memory,  etc.;  but 
though  these  generic  terms  are  convenient,  their  application  to  con- 
crete cases  requires  more  particularization  and  qualification,  as 
already  remarked.  The  attention,  discrimination  and  memory  in- 
volved in  an  example  in  multiplication  are  not  quite  the  same  proc- 
esses as  have  been  studied  in  the  preceding  tests.  For  our  present 
purpose,  the  arithmetical  tests  are  to  be  regarded  simply  as  measures 
of  efficiency  in  a  rather  complex  and  very  practical  sort  of  mental 
work. 

1.  Addition.— Subject  I.,  for  28  days  at  the  periods  shown  in  the 
lowest  part  of  Table  XXIV.,  added  six  columns  (25  figures  each)  as 
rapidly  as  possible,  timing  with  a  stop-watch.  The  average  time  in 
seconds  is  shown.  The  first  six  subjects  used  ten  columns  (15  figures 
each)  :  A  used  six  columns.  Some  correction  was  made  for  practise 
in  the  first  five  days. 


54 


DIURNAL    COURSE    OF   EFFICIENCY 


Table  XXIV.    Addition — Columns  of  15  Figures. 


Subject. 

Total  No.  of 
Columns. 

I. 

140 

II. 

120 

III. 

120 

IV. 

100 

V. 

120 

VI. 

100 

Average. 

117 

A 

84 

7-9  A.M. 
Time.    P.E.    Mis. 


99.4 

110.2 

89.5 

66.3 

105.2 

122.3 


1.00 
1.11 
1.28 
0.55 
0.99 
1.78 


1.2 

0.8 
1.0 
0.6 
1.3 
1.1 


98.8 
112.3 


1.11 
2.4 


1.0 
1.2 


12-2  P.M. 


91.9  0.91  0.6 

99.1  1.44  0.7 

87.3  1.13  0.7 

64.7  0.78  0.8 

90.8  0.81  0.6 
119.4  1.81  1.4 


92.2  1.15  0.6 


5-7  P.M 

Time. 

P.E. 

Mis. 

92.6  0.86 

1.4 

106.9 

1.32  0.9  1 

86.0  0.90  0.7  1 

63.6 

0.78 

0.6 

99.2 

0.88 

1.0 

123.0 

1.58 

1.0 

95.2 

1.06  0.9  1 

106.7 

2.1 

1.1 

9-11  P.M. 
Time.  P.E.  Mis. 


97.0  0.89  0.9 
109.2  1.67  1.1 

8.5.3  0.90  1.5 

69.2  1.52  0.6 

98.8  0.69  1.2 

116.9  1.79  1.2 

96.1  1.24  1.08 
107.6  2.5    1.4 


Cols,  of 
25  Figs. 

I.  150 


7  A.M. 


29.6  0.221.1 


10  A.M. 


1P.M. 


28.4  0.281.0  29.2  0.281.0 


4  P.M. 


7  P.M. 


28.5  0.29  0.8  28.0  0.241.0 


10  P.M. 


31.0  0.291.0 


The  fact  found  here  is  a  higher  efficiency  at  the  noon  period  and 
a  lower  efficiency  in  the  morning  than  at  the  other  periods,  with  the 
usual  individual  divergencies  rather  minimized.  Accuracy  pursues 
the  same  course  as  speed,  which  is  noteworthy  when  compared  with 
its  tendency  in  the  other  tests.  In  the  lower  case  of  subject  I.,  the 
10  A.M.,  1  and  4  p.m.  periods  were  affected  by  occasional  interruption. 

Subject  VII.,  in  an  uncompleted  series  of  four  days,  took  this 
test  at  9  A.M.,  12  m.  and  4  p.m.,  and  made  this  record : 

232  (P.E.,  3.2);  215  (2.1);  227  (2.9). 

Each  member  of  group  B  was  given  24  of  these  15-figure  lists, 
and  240  seconds  in  which  to  add  them.  Their  results  are  expressed 
in  terms  of  the  average  number  of  columns  done  and  the  P.E.: 

15   (1.4);  14   (1.3);  15   (1.3). 

This  is  a  chance  order.  Here,  as  in  memory,  the  first  trial  is  at  a 
disadvantage  because  of  newness  of  the  test,  while  the  others  are  more 
favored  by  practise. 

2.  3Iulti'plication. — In  mental  multiplication,  subject  I.  for 
twelve  days,  under  the  very  favorable  conditions  described  for  the 
German  words  memory  test,  used  two-place  numbers  after  excluding 
0,  1,  2  and  5 — though  5  was  used  in  hard  combinations.  Being  a 
poor  visualize!',  the  author  found  this  to  be  a  sufficiently  difficult 
test.  At  each  period,  three  pairs  (on  some  days  four)  of  such 
numbers  were  multiplied,  and  the  time  taken  as  before. 

The  first  two  are  the  periods  of  highest  ability ;  from  1 :30  p.m. 
to  3  p.m.,  at  6  p.m.  and  again  at  10:30  p.m.  occur  the  points  of 
greatest  inefficiency.  This  very  closely  follows  the  diurnal  curve 
of  subjective  feeling  alluded  to  above.  It  is  nearer  that  for  memory 
than  for  addition,  though  really  comparable  figures  are  not  at  hand. 


COURSE    OF    MENTAL    EFFICIENCY 


55 


The  order  shown  is  heightened  in  validity  when  the  mistakes  are 
also  considered;  there  is  no  inverse  relation  here. 

Table  XXV.    IIental  Multiplication — Numbeks  of  2  Figures. 


Subj. 

No. 

7:00  A.M. 
Time.     P.E.      Mis. 

8:30  A.M. 
Time.     P.E.     Mis. 

10:00  A.M.                   11:30  A.M. 
Time.     P.E.      Mis.  Time.      P.E.     Mis. 

I. 

40 

37.6    2.4      .50 

34.7     1.6     .50 

39.7     2.5     .63   41.8     1.7     .50 

Subj. 

No. 

1:30  P.M. 
Time.     P.E.     Mis. 

3:00  P.M. 
Time.      P.E.     Mis. 

4:30  P.M. 
Time.      P.E.     Mis. 

6:00  P.M. 
Time.      P.E.      Mis. 

I. 

40 

4.80     2.6     .70 

45.3     2.6     .83 

41.0      1.8      .60 

47.1       2.4      .71 

Subj. 


40 


7:30  P.M.  9:00  P.M. 

Time.      P.E.     Mis.  Time.     P.E.     Mis, 


39.8     1.9     .53 


41.7     1. 


.63 


10:30  P.M. 
Time.     P.E.      Mis. 


47.0     2.6      .73 


In  the  following  section  (p.  75),  reference  will  be  made  to  work 
in  addition  done  by  Roemer,  who  finds  the  first  of  four  morning 
periods  the  best;  and  by  Thorndike  (p.  85),  who  also  found  the 
ability  slightly  the  best  then.  The  latter,  in  mental  multiplication, 
found  in  a  very  short  series  the  night  period  a  little  better  for 
adults ;  while  in  written  multiplication  a  very  extensive  test  of 
school  children  (750)  favored  the  morning. 

2.    Translating  French;  Scoring  Death  Becords 

Subject  I.,  under  the  excellent  conditions  of  all-day  experimenta- 
tion described  above,  translated  French  at  seven  different  periods 
of  an  hour  each,  every  day  for  twelve  days.  It  would  seem  at  first 
thought  that  translation  by  mere  reading  is  a  better  test  than  that 
by  writing,  since  the  latter  involves  a  motor  element.  However, 
the  former  is  subject  to  a  subtler  and  no  less  vitiating  complication. 
All  that  one  aira.s  to  do  by  the  reading  method  is  to  get  the  meaning, 
and  that  usually  amounts  to  merely  sensing  the  meaning.  This 
process  is  so  indefinite  and  the  quality  of  the  results  so  indifferently 
estimated  as  to  make  unreliable  all  objective  measurement  based  on 
the  number  of  sentences  thus  subjectively  rendered.  That  is,  the 
work  at  those  periods  of  the  day  when  feelings  of  fatigue  are  most 
pronounced  would  unconsciously  be  slurred  over,  while  at  those 
times  when  one  is  most  conscientiously  sensitive  to  his  duty  it  would 
be  relatively  slow.  The  net  result  would  be  a  lessening  of  the 
diurnal  differences.  No  such  fast-and-loose  interplay  can  well  be 
indulged  in  when  the  product  is  in  sight,  and  for  this  reason  the 
other  method  was  selected.  Scientifically  unsatisfactory,  it  yet  gives 
an  idea  of  what  might  be  expected  in  the  practical  matter  of  written 
translation. 


56  DIURNAL    COURSE    OF   EFFICIENCY 

Table  XXVI.     French  Tkanslation — Sentences  Written  Per  Hour. 


Sub- 
ject. 

9:00-10:00  A.M. 
No.     P.E. 

10:30-11:30 
No.    P.E. 

2:00-3:00  P.M. 
No.     P.E. 

3:30-4:30 
No.    P.E. 

5:00-6:00 
No.    P.E. 

8:00-9:00 
No.    P.E. 

9:30-11:30 
No.    P.E. 

I 

50    0.88 

51      1.03 

54     1.17 

55    0.77 

54    1.12 

56    1.02 

57     0.44 

The  morning  work  is  slowest,  the  afternoon  medium,  and  the 
night  swiftest.  In  accounting  for  the  higher  night  efficiency,  the 
following  factors  seem  to  figure  in  the  result  and  to  be  of  weight  in 
the  order  named :  (1)  quicker  motor  functioning ;  (2)  practise  effect; 
(3)  habit;  (4)  end- glow. 

In  examining  the  36,000  death  records,  reported  earlier  in  the 
paper,  ten  days  were  consumed  by  subject  I.  at  the  New  York  City 
Health  Department  offices.  Work  was  begun  promptly  at  9  a.m. 
and  continued  without  interruption  till  12 :45  p.m.  ;  beginning  at 
1 :15  P.M.  there  was  no  break  till  4  p.m.,  when  the  office  closed.  Dur- 
ing this  time,  tab  was  kept  on  the  exact  number  of  records  handled 
every  fifteen  minutes,  and  the  average  scores  obtained  are  in  the 
following  table.  The  fourth  and  fifth  results  are  estimated  from 
work  of  three  quarters  of  an  hour  in  length. 

Tap.le  XXVII.     Death  Records. 
Average  Number  Examined  Each  Fourth  of  an  Hour. 


j.»'=4,  No.      P.E. 


10  138.6  1.06 


10-11  A.M. 
No.      P.E. 


135.0  1.34 


11-12  A.M. 
No.      P.E. 

12-1  P.M. 
No.      P.E. 

1-2  P.M. 
No.      P.E. 

2-3  P.M. 
No.      P.E. 

133.9  1.23 

131.4  2.39 

133.1  2.11 

130.1  2.03 

3-4  P.M. 
No.     P.E. 

142.1 1.79 


There  is  a  decided  falling  off  after  the  first  hour  which  continues 
till  noon  intermission ;  then  a  slight  recovery,  followed  by  the  lowest 
point  reached,  which  is  itself  succeeded  by  the  highest  point.  This 
curve  can  not  be  said  to  folloAv,  throughout  its  whole  course,  that 
of  any  other  measured  activity  of  this  subject.  This  is  not  odd,  as 
the  operation  involved  was  a  very  complex  one.  Five  things  had  to 
be  noted  in  diff'erent  parts  of  the  death  certificate — cause,  time  and 
season  of  death,  age  and  sex.  While  being  located  properly  on  the 
score  sheets — a  process  again  involving  much  discrimination — they 
had  to  be  carried  in  mind  or  else  a  second  look  was  required.  Judg- 
ment Avas  also  required  in  the  work;  but  memory  and  movement 
were  apparently  the  most  telling  elements  in  determining  the  curve. 
Good  memory  favored  a  strong  beginning  in  the  morning  and  good 
motor  rate  a  strong  ending  in  the  afternoon,  while  the  period  from 
1  p.M  till  3  P.M.  was  specially  unfavorable  to  both.  The  impulse  to 
finish  a  certain  number  before  four  o'clock,  if  possible,  was  always 
too  great  to  be  resisted,  even  Avhen  note  was  taken  of  the  accelerated 


COURSE    OF   MENTAL    EFFICIENCY  57 

rate  and  it  was  felt  that  the  results  were  being  unduly  affected. 
Yet  it  must  be  recalled  that  every  effort  was  made  throughout  the 
day  to  do  the  utmost  possible  consistent  with  accuracy.  End-glow 
has  often  established  its  claim  to  recognition,  but  no  special  practical 
use  of  it  suggests  itself. 

3.    School  Examinations  and  School  Marks 

Rice^  conducted  some  very  extensive  tests  in  spelling  and  arith- 
metic, to  ascertain  the  relative  values  of  different  methods  of  admin- 
istration and  teaching,  and  other  points  of  educational  import.  The 
arithmetical  investigation  was  carried  on  with  6,000  children,  of 
eighteen  schools,  in  seven  cities,  and  consisted  in  giving  certain 
examples  to  be  worked,  the  total  outcome  of  which  was  then  scored 
up  in  several  ways — (a)  per  cent,  correctly  done;  (&)  per  cent,  with 
principle  correct:  (c)  average  number  of  mechanical  errors  made. 
About  half  of  the  tests  were  given  in  the  morning  and  half  in  the 
afternoon. 

As  far  as  Rice's  work  touches  the  present  problem,  his  ideas  are 
fully  set  forth  in  the  following  quotation,  it  being  understood  that 
the  table  referred  to  by  him  shows  only  incidentally  the  times  of  day 
when  the  schools  were  examined,  and  does  not  collate  the  results 
quantitatively  from  this  point  of  view,  which  is  investigated  only 
in  the  desultory  fashion  betokened  by  his  remarks : 

The  idea  is  generally  accepted  that  an  examination  in  arithmetic  given  in 
the  morning  will  show  much  more  favorable  results  than  one  given  in  the 
afternoon,  and  it,  therefore,  might  be  supposed  that  the  schools  that  did  best 
had  been  examined  in  the  morning,  and  vice  versa.  When  the  table  was  ex- 
amined from  this  standpoint  the  indications  appeared  to  favor  the  theory;  but 
the  quantitative  aspect  has  certainly  been  exaggerated.  Looking  at  the  facts 
we  find  that  .  .  .  the  first  three  schools  of  city  I.  were  examined  in  the  morning 
and  did  well.  The  fourth  of  that  city  was  examined  in  the  afternoon  and  also 
did  well.  The  point  of  particular  interest  is  the  fact  that  the  school  by  be- 
ing examined  in  the  afternoon  did  not  lose  its  classification  (rank).  .  .  . 
Thus  while  there  seems  to  be  some  advantage  in  an  examination  in  the  morning, 
the  figures  appear  to  leave  no  doubt  that  a  school  that  can  do  well  in  the  morn- 
ing can  also  do  well  in  the  afternoon,  and  conversely.  ...  I  have  heard  it 
stated  that  the  difference  between  a  morning  and  an  afternoon  examination  will 
probably  reach  20  per  cent. 

His  table  is  extensive,  showing  results  separately  for  each  school 
grade  examined.  By  averaging  together  all  grades  of  each  school, 
the  figures  of  Table  XXVIII.  were  obtained  as  measures  of  the 
different  schools  as  wholes.  Eight  were  examined  in  the  morning 
and  ten  in  the  afternoon ;  to  get  equality,  the  records  of  schools  II. 

^'Educational  Research,'  Forum,  34:   281-297.      1902. 


58 


DIURNAL    COURSE    OF   EFFICIENCY 


and  v.,   falling"  practically   at   the   median   for   all   the   afternoon 
schools,  were  omitted. 

Table  XXVIII.     A  Test  in  Arithmetic — Revision  after  Rice. 


School. 

Morning. 

Afternoon. 

City. 

Work 
Correct. 

Principle 
Correct. 

Mechanical 
Errors. 

WorkI 
Correct. 

Principle 
Correct. 

Mechanical 
Errors. 

III. 

1 

80.0 

83.1 

3.7 

I. 
I. 
I. 
I. 

1 

2 
3 
4 

76.6 
69.3 
67.8 

80.3 
75.1 

72.2 

4.6 

7.7 
6.1 

64.3 

70.3 

8.5 

III. 

2 

54.4 

58.9 

7.1 

IV. 
IV. 
IV. 
IV. 

1 

2 
3 

4 

55.1 
51.5 

58.4 
57.6 

5.6 
10.5 

53.9 

42.8 

58.8 
48.2 

8.3 
11.2 

VI. 
VI. 
VI. 

1 

2 
3 

39.0 

42.9 

9.0 

36.5 
36.0 

43.6 
42.5 

16.2 
15.2 

VII. 
VII. 
VII. 

1 
2 
3 

40.5 

45.9 

11.7 

36.5 
25.3 

40.6 
31.5 

10.1 
19.6 

Averages  of  the  8 
Schools'  Averages. 

60.0 

64.4 

7.4 

43.7 

49.3 

12.1 

A  glance  at  this  table  shows  a  decided  superiority  of  the  morning 
over  the  afternoon  schools,  the  latter  doing  only  about  70  per  cent, 
as  well  as  the  former,  taking  all  three  modes  of  scoring  into  consid- 
eration. This  would  certainly  have  been  observed  by  Dr.  Rice  if 
he  had  thought  it  worth  while  to  make  other  than  a  casual  com- 
parison. Several  of  his  quoted  statements  seem  unhappily  framed, 
in  the  light  of  this  revised  tabulation.  It  may  be  urged  against  this 
revision  that  the  best  cities  were  tested  mostly  in  the  morning  and 
the  poorest  mostly  in  the  afternoon.  Of  course  there  is  no  way  of 
knowing  offhand  whether  this  is  true  or  not,  but  It  wdll  be  found  by 
examination  of  the  table  that  the  percentage  of  difference  still  re- 
mains considerable  when  only  schools  of  the  same  city  are  compared 
wuth  each  other.  When  the  extensiveness  of  the  experiments  and 
the  decisiveness  of  the  results  are  both  considered,  such  figures  have 
no  small  importance  for  the  view  that  children  reach  their  maximal 
period  of  customary  efficiency  earlier  than  adults. 

The  writer  attempted  to  get  school  marks  of  different  classes 
in  the  same  branch,  under  the  same  teacher,  but  meeting  at  different 
times  of  day,  in  the  New  York  City  High  Schools.  Only  one  school 
was  found  in  which  the  conditions  were  favorable.  In  that  about 
fifteen  teachers  had  from  two  to  four  classes  of  the  kind  required, 


COURSE    OF    MEXTAL    EFFICIENCY  59 

and  to  each  of  these  teachers  was  given  written  information  as  to 
the  problem  and  its  pedagogical  bearing,  together  with  the  nature 
of  the  data  desired,  and  a  blank  form  upon  which  the  marks  could 
be  readily  copied.  It  would  have  taken  a  live  teacher  about  fifteen 
minutes  to  transcribe  the  marks  of  four  ordinary  classes,  whereas 
it  took  the  author  a  day — after  getting  the  school  located — to  do  his 
part :  as  result,  one  teacher  responded  with  four  classes. 

Two  first-year  morning  classes  in  botany,  23  pupils  each,  aver- 
aged 62  and  67,  while  two  in  the  afternoon,  of  24  and  25  pupils, 
averaged  61  and  62.  This  vrliole  case  is  introduced  to  show  the  need 
of  a  more  general  and  extensive  sympathy  Avith  scientific  efforts. 
While  07ily  78  per  cent,  of  the  manufacturers  and  80  per  cent,  of 
the  physical  directors  and  athletes  failed  to  make  a  response  of  any 
sort,  92  per  cent,  of  the  educating  class  itself  took  this  frigid  attitude, 
and  that,  too,  when  less  was  individually  required.  The  loss  to 
science  is  not  great  in  regard  to  the  school  marks,  as  the  bases  of 
grading,  with  different  teachers,  are  quite  variable  factors. 

4.  Students'  and  Authors'  Preferred  Hours  for  Work 

The  work  of  0 'Shea's,^  incidentally  mentioned  above,  is  largely 
based  on  the  answers  received  to  a  questionnaire  sent  to  the  students 
of  the  University  of  Wisconsin.  Two  of  the  questions  were — Dur- 
ing what  hours  of  the  day  are  you  at  your  best  ?  and,  Wlien  are  you 
dullest?  The  total  number  of  answers  received  is  not  stated,  but 
the  number  treated  is  316.  To  this  topic,  in  the  text,  he  devotes  little 
more  than  a  page,  from  which  the  following  quotations  are  made : 
"Practically  all  those  who  reported  testified  that  their  minds  worked 
best  in  the  forenoon,  eighteen  reported  being  best  in  the  afternoon, 
Avhile  two  found  that  they  could  accomplish  more  at  five  o'clock  in 
the  morning  than  at  any  other  hour.  The  best  hours  ranged  from 
7  to  12  in  the  forenoon  while  the  choicest  period  of  the  day  is  from 
9  to  11."  It  is  unfortunate  that  the  second  question  was  entirely 
ignored,  though  we  are  just  as  much  interested  in  knowing  its 
answer.     To  thus  omit  half  a  fact  seems  unscientific. 

Quoting  again  (p.  195),  "There  can  be  little  doubt  that  for  most 
people  the  morning  hours  are  most  profitable  to  be  devoted  to  dili- 
gent, concentrated  study.  The  afternoon  hours  can  be  employed 
to  greater  advantage  in  duties  demanding  less  energizing  of  the  will; 
while  in  an  ideal  program  the  evening  hours  will  be  spent  almost 
wholly  in  relaxation.  ...  2  students  reported  not  studying  be- 
yond 8  (at  night)  ;  44  worked  until  9;  187  until  10;  70  until  11; 
9  until  12;  and  1  until  1.    .    .    .    Forty  of  those  who  studied  very 

1' Aspects  of  Mental  Economy,'  Bid.  of  Univ.  of  Wis.,  2:   34-198.      1901. 


60  DIURNAL    COVRSE    OF   EFFICIENCY 

late  into  the  night  testify  that  the  knowledge  they  acquired  stayed 
with  them ;  58  said  that  in  the  morning  it,  like  the  Arab,  had  folded 
its  tent  and  silently  slipped  away." 

This  oriental  allusion  recalls  what  Dr.  J.  M.  Scott,  Professor 
of  Greek  in  Northwestern  University,  recently^  said  so  directly  to 
the  contrary  in  addressing  his  class  on  'burning  the  midnight  oil'. 
"In  olden  days,"  he  stated,  "the  Persians  congregated  at  daybreak 
to  pursue  their  studies;  but  nowadays  the  great  scholars  pore  over 
their  books  at  night.  In  the  morning  one's  eyes  are  not  clear,  his 
head  still  is  numb  from  sleep,  and  he  is  in  no  condition  for  mental 
work.  Because  of  lack  of  illuminating  facilities  the  ancients  w^ere 
obliged  to  study  in  the  early  morning.  Although  I  would  not  urge 
any  of  you  to  refrain  from  rising  early,  I  would  advise  you  to  do 
your  studying  at  night," 

It  is  a  question  for  serious  consideration  whether  an  occasional 
sacrifice  to  overstudy  should  not  be  made  rather  than  that  such  an 
arbitrary  rule  of  ten  o'clock  retirement  should  be  imposed  as  exists 
at  most  of  our  women's  colleges.  When  one  gets  'into  the  swing' 
he  can  often  accomplish  more  in  six  or  eight  consecutive  hours  .of 
night  work  than  in  double  that  number  of  hours  of  day  work  done  in 
bits,  as  it  often  is.  Whenever  a  person  can  work  with  the  least 
expenditure  of  energy  is  the  proper  time  for  him  to  do  so.*  There 
seems  no  more  reason  in  trying  to  fit  all  types  of  students  to  one 
sort  of  study-hour  jacket  than  in  attempting  to  place  one  kind  of 
instruction-plan  coat  upon  all  kinds  of  developing  individualities. 
Authors  have  learned  this  general  fact  by  experience  and  take  ad- 
vantage of  it  in  their  work,  if  the  following  account  of  them  is 
typical,  as  it  seems  to  be. 

Hundreds  of  biographies''  were  scanned  for  the  occasional  words 
treating  the  matter  of  authors'  preferred  hours  for  composition. 
Some  160,  odd,  cases  w^ere  found,  definite  enough  for  accurate  use, 
and  of  these  160,  even,  of  the  best  were  selected  for  reporting  hei'e. 
These  distributed  themselves  diurnally  in  this  manner:  morning 
composers  (6  a.m.  to  2  p.m.),  55,  or  34  per  cent.;  afternoon  (2  to 
7  P.M.),  2,  or  1  per  cent.;  night  (7  to  12  p.m.),  17,  or  12  per  cent.; 
after  midnight  (12  to  6  a.m.),  9,  or  6  per  cent.;  moniing  and  after- 
noon (6  A.M.  to  7  p.m.),  27,  or  17  per  cent.;  morning  and  night  (6 

1  March  24,  190.5. 

*  See  Hamerton's  Intellectual  Life,  pp.  380-400,  for  instructive  treatment 
of  this  question. 

3  About  100  volumes  were  examined  in  this  search.  The  two  of  most  value 
were  Dr.  Hugo  Erichsen's  Methods  of  Authors,  1894,  and  Aspects  of  Authorship, 
by  F.  Jacox,  1872. 


COURSE    OF    MENTAL    EFFICIENCY  61 

A.M.  to  2  P.M.  and  7  to  12  p.m.),  6,  or  4  per  cent.;  afternoon  and 
night  (2  to  12  p.m.),  4,  or  3  per  cent;  whole  day  (6  a.m.  to  12  p.m.), 
37,  or  23  per  cent.  Some  writers  were  included  whose  actual  work- 
ing hours  were  secured,  but  not  their  expressly  preferred  hours. 
Some,  who  were  assigned  to  the  first,  fifth  or  last  group,  might 
almost  as  correctly  have  been  put  in  the  'night'  group,  for  one  reason 
and  another,  and  this  would  raise  the  percentage  of  the  latter  some- 
what. Secondary  preferences  are  shown  in  parentheses  in  the  de- 
tailed list  now  to  be  given.  The  chief  field  of  each  one's  activities 
is  only  partially  indicated  in  most  of  the  cases.  The  letter  F,  in 
parentheses,  means  'female.'     The  lists  are  arranged  alphabetically. 

Morning:  J.  Addison  (Eng.  essayist),  G.  von  Amyntor  (Ger. 
novelist),  L.  A.  Banks  (Am.  clergyman  and  author),  V.  Bliithgen 
(Ger.  novelist — night),  C.  Bronte  (Eng.  novelist  and  poet — F), 
E.  Bronte  (Eng.  novelist  and  poet — F),  M.  Cawein  (Am.  poet), 
T.  Chalmers  (Eng.  theologian  and  journalist),  G.  M.  Craik  (Eng. 
novelist— i^),  C.  Deslys  (Fr.  novelist),  C.  Dickens  (Eng.  novelist), 
J.  Drj^den  (Eng.  poet),  R.  W.  Emerson  (Am.  philosopher  and  essay- 
ist—night), M.  Eytinge  ( poet  and  novelist— i^),  K.  Field  (Am. 

novelist — F),  K.  Frenzel  (Ger.  journalist — night),  0.  F.  Genischen 
(Ger.  dramatist),  E.  Gibbon  (Eng.  historian),  J.  W.  Goethe  (Ger. 
poet),  E.  Gosse  (Eng.  poet  and  critic — night),  E.  E.  Hale  (Am. 
essayist),  R.  Hamerliug  (Austrian  novelist),  0.  W.  Holmes  (Am. 
poet  and  humorist),  W.  D.  Howeils  (Am.  novelist),  V.  Hugo  (Fr. 
novelist),  L.  Hunt  (Eng.  poet— night),  W.  Irving  (Am.  novelist), 
D.  W.  Jerrold  (Eng.  dramatist  and  journalist — night),  I.  Kant 
(Ger.  philosopher),  T.  B.  Macaulay  (Eng.  essayist),  H.  Martineau 
(Eng.  novelist— i^),  (J.)  B.  Matthews  (Am.  dramatist  and  critic- 
night),  J.  Miller  (Am.  poet),  J.  Milton  (Eng.  poet— afternoon), 
A.  Niemann  (Ger.  novelist),  A.  Pope  (Eng.  poet— day),  L.  de  la 
Ramee  (Eng,  novelist— i*^) ,  E.  Richebourg  (Fr.  novelist),  J.  P. 
Richter  (Ger.  poet),  L.  de  Sacher-Masoch  (Fr.  story  writer — after- 
noon), J.  Scherr  (Swiss  novelist  and  historian),  Sir  W.  Scott  (Eng. 
novelist),  W.  G.  Simms  (Am.  poet— night),  F.  R,  Stockton  (Am, 
novelist),  J.  Taylor  (Eng.  poet  and  novelist— F),  W,  M.  Thackeray 
(Eng.  novelist),  A.  Thuriet  (Fr.  novelist),  M.  Thompson  (Am.  critic 
and  essayist),  E.  Vely  (Ger.  novelist — F),  P.  Virgil  (Latin  poet), 
R.  AYaldmueller  (Ger.  novelist),  D.  Webster  (Am.  statesman),  E. 
Wichert  (Ger.  novelist),  C.  M.  Yonge  (Eng.  novelist— F),  C.  Kings- 
ley  (Eng.  clergyman  and  novelist— night). 

Afternoon:   S.   0.   Jewett    (Am.   story  writer— i^),   A.    Traeger 
(Ger.  poet). 
5 


62  DIURNAL    COURSE    OF   EFFICIENCY 

Night:  V.  Alfieri  (Italian  dramatist),  W.  B.  Blake  (Eng.  poet- 
after  midnight),  K.  S.  Bonner  (Am.  story  writer  and  novelist — F), 
R.  S.  Cabanis  (Ger.  humorist— after  midnight),  Wm.  Collins  (Eng. 
poet),  J.  Fastenrath  (Ger.  and  Span,  poet),  R.  E.  Franeillon  (Fr. 
novelist  and  journalist— afternoon),  F.  Friedrieh  (Ger.  novelist), 
W.  A.  Hammond  (Am.  novelist — after  midnight),  T.  Hardy  (Eng. 
novelist— day),  J.  C.  Harris  (Am.  humorist  and  journalist— day), 
H.  Herberg  (Ger.  novelist),  T.  Hood  (Eng.  poet  and  humorist- 
day),  S.  Johnson  (Eng.  essayist  and  lexicographer— day),  C.  Lamb 
(Eng.  poet— after  midnight),  M.  J.  Preston  (Am.  poet— F),  S. 
Rogers  (Eng.  poet),  P.  K.  Rossegger  (Austrian  novelist),  R.  B. 
Sheridan  (Eng.  dramatist),  R.  Southey  (Eng.  poet— day). 

After  midnight:  H.  de  Balzac  (Fr.  novelist).  Lord  Byron  (Eng. 
poet),  S.  T.  Coleridge  (Eng.  poet),  T.  De  Quincey  (Eng.  essayist), 
J.  Fane  (Eng.  poet).  Lord  Jeffrey  (Eng.  poet),  E.  A.  Poe  (Am.  poet 
and  story  writer),  H.  Rollet  (Austrian  poet— night),  F.  Schiller 
(Ger.  poet— night). 

Morning  a7id  afternoon:  L.  Anzengruber  (Austrian  story  writer), 
R.  Baumbach  (Austrian  poet),  J.  Burroughs  (Am.  naturalist),  T. 
Carljde  (Scot,  essayist  and  historian),  J.  Claretie  (Fr.  novelist), 
M.  D.  Conway  (Am.  essayist),  F.  Dahn  (Ger.  historian  and  poet), 
G.  M.  Fenn  (Eng.  novelist),  P.  Galen  (Ger.  novelist— night),  A. 
Glaser  (Ger.  novelist — night),  R.  von  Gottschall  (Ger.  novelist  and 
journalist),  M.  Greif  (Ger.  poet),  L.  Habicht  (Ger.  novelist),  T.  "W. 
Higginson  (Am.  novelist  and  essayist),  L.  Larcom  (Am.  poet— i^), 
H.  Malot  (Fr.  novelist),  T.  Moore  (Eng.  poet),  J.  Nordmann  (Ger. 
novelist  and  journalist),  U.  Prynne  (Eng.  controversialist),  "VV.  H. 
Riehl  (Ger.  novelist),  E.  P.  Roe  (Am.  novelist— night),  J.  Stinde 
(Ger.  satirist),  C.  Thaxter  (Am.  poet— F),  J.  T.  Trowbridge  (Am. 
novelist),  J.  G.  Whittier  (Am.  poet),  A.  von  Winterfeld  (Ger. 
humorist),  J.  Wolff e  (Ger.  poet). 

Morning  and  night:  R.  Burns  (Scot,  poet),  0.  Goldsmith  (Eng. 
poet  and  novelist),  N.  Hawthorne  (Am.  novelist),  Plato  (Gr.  philos- 
opher), F.  W.  Robertson  (Scot,  clergyman  and  author),  S.  Smith 
(Eng.  poet  and  critic). 

Afternoon  and  flight:  T.  Campbell  (Scottish  poet  and  novelist), 
W.  Hazlitt  (Eng.  critic  and  essayist),  J.  Rousseau  (Fr.  philosopher 
and  educator),  A.  Streckfuss  (Ger.  novelist). 

Whole  day:  L.  M.  Alcott  (Am.  novelist— i^),  H.  H.  Bancroft 
(Am.  historian)  'Venerable  Bede'  (Eng.  author),  E.  Bulwer-Lytton 
(Eng.  novelist  and  poet),  W.  Carleton  (Am.  poet),  T.  Carte  (Eng. 
historian),  Wilkie  Collins  (Eng.  novelist),  Delambre  (Fr.  philos- 
opher), A.  L.  G.  N.  De  Stael   (Fr.  novelist-i^),  G.  Ebers   (Ger. 


COURSE    OF    MENTAL    EFFICIENCY  63 

novelist— night),  J.  Fiske  (Am.  historian  and  essayist),  P,  H.  Hayne 
(Am.  poet),  J,  Hogg  (Scot,  poet  and  biographer),  J.  Keats  (Eng. 
poet),  W.  S.  Landor  (Eng.  poet),  S.  Lanier  (Am.  poet  and  novelist), 
0.  von  Leixner  (Ger.  poet,  historian  and  novelist — night),  P.  Lindau 
(Ger.  novelist),  H.  AV.  Longfellow  (Am.  poet),  Mazerai  (Aus.  his- 
torian), A.  Meissner  (Austrian  novelist— night),  J.  L.  Motley  (Am. 
historian),  J.  Payn  (Eng.  novelist),  F.  Petrarch  (Italian  ecclesiast 
and  poet),  W.  H.  Prescott  (Am.  historian),  B.  W.  Proctor  (Eng. 
poet),  F.  Rabelais  (Fr.  educator  and  humorist),  L.  von  Ranke  (Ger. 
historian),  J.  W.  Riley  (Am.  poet),  W.  Robertson  (Eng.  historian), 
P.  B.  Shelley  (Eng.  poet),  K.  Stelter  (Ger.  poet— night),  H.  B. 
Stowe  (Am.  novelist— i^) ,  H.  D,  Thoreau  (Am.  author),  E.  M. 
Vacano  (Ital.  author),  J.  Wilson  (Scot,  essayist,  novelist  and  poet), 
W.  AVordsworth  (Eng.  poet). 

Numerically,  morning  stands  easily  in  the  lead  among  the  different 
groups,  and  this  precedence  might  be  emphasized  if  those  persons 
could  be  segregated  from  the  fifth,  sixth  and  eighth  groups  who 
were  obliged  by  financial  necessity,  or  social  custom,  to  scatter  their 
work  over  such  extensive  periods  of  the  day. 

But  an  accurate  estimate  of  the  night  workers  will  show  this 
general  group  a  closer  second  to  the  former  than  appears  at  first 
sight.  Again  we  must  make  allowance  for  those  included  in  groups 
6,  7  and  8  who  would  preferably  work  only  at  night  if  composition 
depended  only  on  inclination.  Fourteen,  outside  of  the  distinctively 
night  groups,  have  indicated  a  night  choice,  and  should  likely  be 
classed  there,  as  they  have  for  the  most  part  stated  that  this  period 
seemed  the  best  for  the  '  creative '  part  of  their  labor,  at  least,  or  was 
preferred  in  early  life.  Psychologically,  it  may  not  be  entirely  true 
that  imaginative  work  is  more  creative  than  certain  other  kinds,  but 
it  is  usually  so  considered  among  the  writers  themselves. 

If  we  take  the  'internal  evidence'  of  the  groups  themselves,  it  is 
possible  to  get  a  little  added  light  on  this  matter  of  the  best  times 
for  different  sorts  of  composition.  That  is,  if  the  poets  and  novelists 
are  roughly  designated  as  an  imaginative  class,  and  the  historians, 
clergymen,  essayists,  critics,  journalists,  philosophers,  etc.,  as  a 
broader,  intellective  class,  we  shall  find  the  former  predominant  in 
the  morning  and  night  groups  and  the  latter  in  the  day  ones.  Entire 
confidence  can  not  be  placed  in  this  division,  as  the  original  assign- 
ment of  'fields  of  activity'  to  the  various  writers  is  not  thoroughly 
exact,  in  that  it  is  much  too  limited  per  individual.  But  certain 
special  groups  tend  to  confirm  the  conclusion.  Thus,  of  thirteen  his- 
torians mentioned,  eleven  occur  in  the  all-day  section;  and  of  the 


64  DIURNAL    COURSE    OF   EFFICIENCY 

after-midnight   workers    all    are    of   the    imaginative   type— if   De 
Quincey  's  product  is  allowed  to  be  prose-poetry,  as  it  is  often  styled. 

While  the  theory  that  night  furnishes  the  best  time  for  original 
composition  is  thus  at  least  strongly  suggested,  it  seems  to  the  pres- 
ent writer  lacking  in  ground  to  support  such  extreme  views  as  have 
been  advanced  by  some.  De  Quincey  is  authority  for  this  state- 
ment of  C.  Lamb:  "No  true  poem  ever  owed  its  birth  to  the  sun's 
light.  The  mild  internal  light,  that  reveals  the  fine  shapings  of 
poetry,  like  fires  on  the  domestic  hearth,  goes  out  in  the  sunshine. 
Milton's  Morning  Hymn  in  Paradise,  we  would  hold  a  good  wager, 
was  penned  at  midnight,  and  Taylor's  rich  description  of  a  sun- 
rise smells  decidedly  of  a  taper."  This  view,  besides  being 
worded  possibly  for  effect,  is  influenced  by  his  own  actual  prac- 
tise in  regard  to  night  work.  Erichsen,  alluded  to  above,  is  a 
whole-hearted  convert  to  the  theory,  though  no  little  could  be 
cited  against  its  unconditional  adoption  from  his  own  book. 
He  remarks  that  Lamb's  tasks  "courted  the  aid  of  evening,  which 
by  means  of  physical  weariness  produces  a  more  luxurious  state 
of  repose  than  belongs  to  the  labor  hours  of  day.  .  .  .  They 
[the  words  'physical  weariness']  almost  exactly  define  that  un- 
natural condition  of  the  body  which  on  other  grounds  appears  to 
be  proper  to  the  unnatural  exertion  of  the  mind."  The  extent  to 
which  he  carries  the  latter  idea  may  be  gathered  from  a  reference 
of  his  to  Scott,  in  another  connection.  Scott  had  said  of  his  own 
review  of  Ritson's  Caledonian  Annals  that  "no  one  who  has  not 
labored  as  I  have  done  on  imaginary  topics  can  judge  of  the  comfort 
afforded  by  walking  on  all  fours,  and  being  grave  and  dull. "  ' '  There 
spoke  the  man,"  says  Erichsen,  "who  habitually  and  without  arti- 
ficial help  drew  upon  his  imagination  at  the  hours  (in  the  morning) 
when  instinct  has  told  others  that  they  should  be  emploj-ing,  not 
their  fancy,  but  their  reason.  So  Scott  compelled  himself  to  do 
unliealthy  or  abnormal  work  without  the  congenial  help  of  abnormal 
conditions. ' ' 

Such  ideas  quite  ignore  the  fact  of  individual  differences— that 
many  have  accomplished  as  good  work  in  the  daytime  as  those  who 
wrote  at  night.  They  also  ignore  the  negative  opinions  of  other 
writers  couched  in  as  positive  terms  as  the  preceding.  Only  one  of 
these,  having  more  empirical  basis  than  the  rest,  will  be  mentioned. 
G.  M.  Fenn,  shoMm  in  the  above  morning-afternoon  list,  after  experi- 
menting with  different  methods  for  some  years,  off  and  on,  decidedly 
prefers  the  daytime.  He  admits  that  brilliant  work  has  often  been 
done  at  night,  but,  after  trial,  found  the  results  of  a  month's  day 
work  more  satisfactory  than  an  equivalent  period  of  night  work. 


COURSE    OF    MENTAL    EFFICIENCY  65 

Parenthetically  it  may  be  noted  here  that  the  last  reference  sug- 
gests the  practical  problem  of  how  far  regular  habits  of  work  have 
proven  beneficial,  compared  with  mere  mood-composition.  My  notes, 
having  bearing  on  this,  are  too  numerous  to  make  it  worth  taking 
up  in  the  short  space  to  which  it  would  have  to  be  confined.^  This 
much  seems  true,  however,  that  the  night  workers  tend  markedly  to 
be  mood-workers,  while  those  of  the  day  tend  more  to  regularity  in 
production.  But  that  the  quality  of  the  latter  work  is  better  is  not 
true,  though  the  quantity  may  possibly  be  greater. 

Before  giving  my  own  general  view  on  the  matter  of  the  pre- 
ceding paragraphs,  the  following  passage  from  a  letter  of  F.  W. 
Robertson,*  who  is  listed  in  the  day-night  group  above,  will  be  of 
some  interest.  "Midday  is  like  mid-life — full  of  commonplace,  of 
toil  and  with  less  of  romance.  .  .  .  Morning  and  evening  correspond 
with  youth  and  age,  in  both  of  which  there  is  a  peculiar  poetry.  .  .  . 
Heaven  lies  around  us  in  our  infancy,  and  I  suppose  the  mystery  of 
the  grave  brings  heaven  again  around  our  decadence,  just  as  the  sun 
approaches  the  horizon  again  at  evening."  He  thinks  the  wonder 
and  mystery  may  seem  lacking  at  midday  because  the  sun  is  directly 

*For  very  many  years  (30-50),  so  it  is  said,  the  villager  of  Konigsberg  was 
wont  to  set  his  watch  by  the  unvarying  appearance  of  Kant  for  his  daily  walk. 
Whether  the  latter's  production  could  have  been  so  well  sustained  without  this 
regularity  one  is  inclined  in  his  case  to  answer  in  the  negative.  Chalmers  was 
another  shining  illustration  of  the  methodical  worker.  It  is  said  that  "  so  far 
before  him  could  he  see,  and  so  methodically  did  he  proceed,  that  he  could 
calculate  for  weeks  and  months  beforehand  the  rate  of  his  progress  and  the 
day  when  each  separate  composition  would  be  finished."  "  His  taste  for 
numerical  arrangement  was  exhibited  in  the  most  insignificant  actions  and 
habits  of  his  life.  It  regulated  every  part  of  his  toilet — down  even  to  the  daily 
stropping  of  his  razor.  .  .  .  He  did  almost  everything  by  numbers.  His 
staff  was  put  down  regularly  at  every  fourth  footfall;  and  the  number  of  its 
descents  gave  an  accurate  measure  of  the  space  over  which  he  had  walked. 
Habit  had  rendered  count  an  easy,  almost  mechanical,  operation;  so  that, 
though  meeting  friends,  and  sustaining  animated  conversation,  it  still  went 
on."  Among  the  imaginative  authors,  Anthony  Trollope  stands  as  the  repre- 
sentative of  composing  by  the  watch,  which  he  literally  did.  Says  he :  "I 
have  always  prepared  a  diary,  divided  into  weeks,  and  carried  it  on  for  the 
time  I  have  allowed  myself  for  the  work.  In  this  I  have  entered  day  by  day 
the  number  of  pages  written,  so  that  if  at  any  time  I  have  slipped  into  idleness 
the  record  stares  me  in  th?  face  and  demands  increased  labor."  And  this  he 
does  "  whether  other  business  is  heavj'  or  light,  or  Avhether  the  book  is  wanted 
with  speed  or  not."  .  .  .  Much  dispute  arose  as  to  the  quality  of  TroUope's 
work,  partly  prejudiced  by  his  thus  violently  flying  into  the  face  of  '  inspira- 
tion,' but  a  just  Clitic  must  grant  that  his  novels  are  not  lacking  in  real 
imaginative  character. 

2  S.  A.  Brooke,  Life  and  Letters  of  F.  W.  Robertson,  1:   341-342.      1865. 


66  DIURNAL    COURSE    OF   EFFICIENCY 

above  and  unseen  then,  and  seem  more  present  at  the  other  periods 
because  it  is  more  visible  then. 

If  we  admit  the  fact  of  a  noticeable  tendency  toward  the  selection 
of  night  for  the  creative  types  of  composition,  it  seems  to  me  that 
the  underlying  causes,  as  far  as  not  concerned  simply  with  the  chance 
distribution  of  individual  differences  that  obtains  in  all  human 
activities,  are  more  extensive  than  either  of  the  foregoing  explana- 
tions implies.  Not  only  'physical  fatigue' — often  exhibited  in  'high- 
strung'  persons  as  nervous  excitation,  as  well  as  'luxurious  repose' 
in  others— and  mysterious  solar  influences,  appear  as  factors,  but 
the  greater  quiet  and  darkness  and  the  heavenly  phenomena— all  with 
their  indefinable  associations,  the  prevailing  social  customs,  and  the 
use  of  artificial  stimulants,  should  not  be  overlooked. 

The  first  of  this  last  set  of  causes  needs  no  lengthy  discussion. 
AVe  are  all  probably  more  affected  by  such  associations  than  we  our- 
selves are  consciously  aware.  Such  influences  as  are  apt  to  affect 
impressionable  temperaments  at  that  time  are  most  admirably  sug- 
gested by  the  following  extract  from  Cable,  giving  the  local  and 
temporal  setting  of  his  novel,  'Madame  Delphine':  "A  beautiful 
summer  night,  when  all  nature  seemed  hushed  in  ecstasy,  one  of  those 
Southern  nights  under  whose  spell  all  the  sterner  energies  of  the 
mind  cloak  themselves  and  lie  down  in  bivouac,  and  the  fancy  and 
the  imagination,  that  can  not  sleep,  slip  their  fetter  and  escape, 
beckoned  away  from  behind  every  flowering  bush  and  sweet-smelling 
tree,  and  every  stretch  of  lonely,  half-lighted  walk,  by  the  genius 
of  poetry. ' ' 

The  second  and  third  causes  bring  me  to  the  expression  of  the 
general  thesis,  which  is  only  this :  that  excitation  of  some  sort  is  most 
often  the  precondition  of  the  highest  imaginative  work.  That  one's 
wits — to  speak  popularly — are  sharpened  by  either  enlightening  or 
enlivening  conversation,  and  that  immediately  subsequent  pen-w^ork 
is  rendered  correspondingly  easier,  will  scarcely  be  disputed,  if  indi- 
vidual cases  of  over-excitement  be  excluded. 

And  that  the  prevailing  social  customs  have  much  favored  this 
sort  of  excitation  may  be  inferred  from  remarks  of  the  following 
tenor.  John  Wilson^:  "In  Dumfries,  as  in  every  other  considerable 
town  in  Scotland— and  we  might  add  in  England— it  Avas  then  cus- 
tomary, you  know,  with  the  respectable  inhabitants,  to  pass  a  con- 
vivial hour  or  two  of  an  evening  in  some  decent  tavern  or  other.  .  .  . 
The  w^orthy  townsfolk  did  not  frequent  bar  or  parlor  or  club-room 
—at  least  they  did  not  think  they  did— from  a  desire  for  drink, 
though  they  doubtless  took  a  glass  more  than  they  intended,  nay, 

^  Genius  and  Character  of  Robert  Burns,   161.    1861. 


COURSE    OF    ME\TAL    EFFICIENCY  67 

sometimes  even  two;  and  the  prevalence  of  such  a  system  of  social 
life,  for  it  was  no  less,  must  have  given  rise,  with  others  besides  the 
predisposed,  to  very  hurtful  habits.  They  met  to  expatiate  and 
confer  on  state  affairs,  to  read  the  newspapers,  to  talk  a  little 
scandal,  and  so  forth,  and  the  net  result  was,  we  have  been  told,  con- 
siderable dissipation."  A  number  of  citations  of  individual  eases, 
in  confirmation  of  the  wide  occurrence  of  this  custom,  could  be  as- 
sembled, if  space  permitted.^ 

Even  less  mention  can  be  made,  or  special  illustration  given,  of 
the  other  numerous  and  well-patronized  methods  of  mental  stimula- 
tion—  from  ordinary  walking,  riding  or  music  to  hourly  service  of 
blackest  coffee,  greenest  tea  or  strongest  opium,  or  to  constant  use 
of  tobacco,  before  and  during  composition.  The  extensiveness  of 
this  among  the  imaginative  writers  is  striking.  While  these  customs, 
or  even  the  most  radical  of  them,  are  not  confined  to  the  night  con- 
tingent of  the  army  of  the  quill,  they  are  most  notably  represented 
there.  Perhaps  a  verj^  slight  basis  of  this  may  lie  in  the  fact  that, 
if  one  felt  some  social  odium  or  attribution  of  weakness  might  attach 
to  over-indulgence  in  these  directions,  it  would  be  easier  and  more 
politic  to  maintain  them  at  night  than  at  any  other  time.  This  would 
also  be  favored  by  the  closely  succeeding  chance  of  'sleeping  off'  ill 
effects  that  might  otherwise  be  distressing. 

The  data  here  are  not  voluminous  nor  reliable  enough  to  make 
possible  any  scientific  determination  of  the  extent  to  which  the  vari- 
ous factors  are  individually  involved  in  the  apparent  special  prefer- 
ence for  night-time  by  imaginative  writers,  and  how  far  it  is  a  purely 
instinctive  inclination.  The  information  necessary  to  the  solution 
of  this  may  some  time  be  at  hand,  but  at  present  we  are  only  in  pos- 

^  Extempore  rhyming,  once  so  popular  in  parts  of  Italy,  in  reference  to  our 
problem  has  bearing  on  both  evening  composition  and  external  excitation. 
This  description — much  shortened — is  to  be  found  in  Spence's  Observations, 
Anecdotes  and  Characters,  pp.  248-251:  "The  improvise  .  .  .  poets  in 
Italy  are  actually  what  they  are  called  .  .  .  and  do  it  with  great  emulation 
and  warmth,  generally  in  octaves,  in  which  the  answerer  is  obliged  to  form 
his  octave  to  the  concluding  line  of  the  challenger;  so  that  all  the  octaves 
after  the  first  must  be  extempore,  unless  they  act  in  concert  together.  Our 
method  is  to  create  our  thought  at  the  enemy's  seventh  verse :  then  we  have  the 
idea,  the  rhymes,  the  words  and  the  verse  to  think  of,  only  while  our  opponent 
is  repeating  his  last  line,  v.hich  we  take  no  manner  of  notice  of  at  all.  We 
almost  always  do  better  the  second  half  hour  than  the  first,  because  one  grows 
warmer  and  warmer,  to  such  a  degree  at  last  that,  when  I  have  improvised  all 
evening,  I  can  never  get  a  wink  of  sleep  all  the  night  after.  .  .  .  Cavalier 
Perfetti,  of  Sienna,  the  best  in  Italy  at  present,  ...  is  so  impetuous  in 
improvising  that  sometimes  he  will  not  give  way  for  the  guitar"  (Signor 
Nanechi) . 


68  DIURNAL    COURSE    OF    EFFICIENCY 

session  of  the  practical  fact  that  many  writers  do  actually  prefer, 
use  and  do  their  best  work  in,  the  night  hours. 

A  noteworthy  exception  to  this  fact  is  found  in  the  case  of  the  fe- 
male authors,  indicated  in  the  above  lists  by  F.  In  all  there  are  18, 
distributed  as  follows :  10,  morning ;  1,  afternoon ;  2,  night ;  2,  morn- 
ing-afternoon;  3,  whole  day.  Remembering  that  the  last  five  belong 
partly  in  the  first  group,  and  that  the  night  groups  have  slight  rep- 
resentation, it  will  be  seen  that  the  early  hours  of  the  day  are  de- 
cidedly in  the  ascendency  as  to  preference.  This  is  quite  in  harmony 
with  what  has  preceded,  in  this  paper,  regarding  the  peculiarities  of 
the  female  diurnal  curve. 

Many  individual  incidents,  of  intrinsic  interest  and  of  some  scien- 
tific value,  must  be  omitted;  but  two  short  instances  of  what  is  re- 
ferred to  may  be  transcribed.  T.  J.  Hogg/  reports  of  Shelley  that 
"at  6  P.M.  he  would  suddenly  compose  himself,  even  in  the  midst  of 
a  most  animated  narrative  or  of  earnest  discussion ;  and  he  would  lie 
buried  in  entire  forgetfulness,  in  a  sweet  and  mighty  oblivion,  until 
10,  when  he  would  suddenly  start  up,  and  rubbing  his  eyes  with  great 
violence,  and  passing  his  fingers  swiftly  through  his  long  hair,  would 
enter  at  once  into  a  vehement  argument,  or  begin  to  recite  verses  .  .  . 
with  a  rapidity  and  an  energy  that  were  often  quite  painful. ' '  Sir 
Walter  Scott-  was  furnished  by  Comte  cle  Tressan  with  this  descrip- 
tion of  the  late  days  of  A,  R.  Le  Sage,  the  noted  French  novelist: 
"Mons.  Le  Sage,  awakening  every  morning  as  soon  as  the  sun  ap- 
peared some  degrees  above  the  horizon,  became  animated,  acquired 
feeling  and  force  in  proportion  as  that  planet  approached  the 
meridian ;  but  as  the  sun  began  to  decline,  the  sensibility  of  the  old 
man,  the  light  of  his  intellect,  and  the  activity  of  his  bodily  organs, 
began  to  diminish  in  proportion ;  and  no  sooner  had  the  sun  de- 
scended some  degrees  below  the  horizon,  than  he  sunk  into  a  lethargy, 
from  which  it  was  difficult  to  arouse  him."  This,  if  true,  is  cer- 
tainly a  remarkable  instance  of  diurnal  rhythm. 

This  must  close  our  account  with  the  authors.  On  the  whole,  it 
appears  that  they  elect  the  hours  most  frequently  used  by  students 
for  their  study, ^  It  is  possible  that  we  have  here  suggested,  not  the 
most  'ideal'  program,  but  the  most  practical  one.     For  those  who 

^Quoted  by  E.  T.  Mason  in  Personal  Traits  of  British  Authors,  1:  110. 
1885. 

^  Lives  of  Eminent  Novelists  and  Dramatists,  596.      Undated. 

'  It  was  said  above  that  some  writers  were  included  whose  actual  working 
hours  were  used,  in  lieu  of  a  distinctive  preference.  By  far  the  larger  part  of 
these  occur  in  the  two  longest  day  groups,  and  especially  in  the  whole-day  group. 
The  percentage  of  the  latter  group  is  thus  too  higli  and  the  others — particularly 
morning  and  night,  as  judged  from  known  cases — are  correspondingly  too  low. 


COURSE    OF    MENTAL    EFFICIEXCY  69 

can  not  stand  a  sixteen-hour  stretch,  it  may  be  better  to  put  the 
relaxative  period  as  an  interlude  rather  than  as  a  postlude.  Pro- 
ductively, whether  a  period  of  relaxation  in  the  midst  of  the  day's 
work  is  good  or  bad  depends  on  the  individual  make-up  and  can  not 
be  judg-ed  aside  from  that;  but  the  'productive'  standpoint  is  the 
best  one  to  take,  if  it  be  true  that  'we  live  in  deeds  and  not  in  years.' 
Productively,  if  not  indeed  constitutionally  also,  too  much  rest  is  as 
injurious  as  too  much  work.  The  fact  is  frequently  overlooked  that 
much  rest,  habitually  indulged  in,  tends  to  beget  a  more-rest  disposi- 
tion, just  as,  so  the  economic  moralists  tell  us,  a  person's  needs  are 
likely  to  increase  with  his  wealth.  It  is  important  to  remember  that 
the  psychological  phenomenon  of  practise  effect  acts  in  rest  and 
work  in  general  just  as  it  does  in  the  particular  manifestations  we 
have  been  dealing  with  above.  In  either  instance,  a  limiting  level  of 
productivity  is  eventually  reached.  In  most  lives  these  matters  are 
left  to  regulate  themselves,  without  a  great  amount  of  conscious  or 
systematic  direction.  We  make  ourselves  believe  that  this  is  always 
due  to  external  conditions,  but  we  have  examples,  several  of  which 
were  mentioned  above,  of  lives  successfully  ordered  by  intelligent 
choice.  The  poetic  temperament  is  peculiar  and  such  regularity 
would  be  unusual  and  possibly  disastrous  in  many  cases,  but  with  all 
persons  it  is  probable  that  more  thought  and  self-experimentation 
along  this  line  would  result  beneficially. 

No  other  pertinent  work  on  the  diurnal  course  of  mental  efficiency 
has  been  found  save  that  to  be  cited  under  '  fatigue. '  The  testing  of 
such  mental  complexes  as  have  been  referred  to  is  deemed  impor- 
tant in  proportion  to  the  homogeneity  of  the  tested  group,  and  the 
preceding  discussion  has  been  limited  for  the  most  part  to  persons 
possessing  considerable  intellectual  culture.  Psychologically  it  would 
be  valuable  if  tests  were  devised  which  would  place  on  a  comparable 
basis  the  mental  operations  of  classes  widely  variant.  This  might 
lead  to  some  fundamental  knowledge  as  to  the  existence  or  non- 
existence of  certain  general  or  essential  forms  of  mental  process,  and 
of  their  kinds,  degrees,  relations,  etc.,  in  any  given  activity. 


III.    Brief  Summary 

It  is  clear  that  whatever  conclusions  are  made,  respecting  the 
data  in  this  section,  will  be  less  firm  than  those  of  the  one  preceding. 
Still,  there  are  some  definite  indications.  As  to  the  simpler  mental 
functions  first  mentioned,  one  would  infer  that  those  which  in  their 
testing  involve  the  use  of  motor  elements  tend  to  follow  in  speed  the 
motor  type  of  midday  maximum,  though  making  it  a  little  earlier, 


70  DIURNAL    COURSE    OF   EFFICIENCY 

while  in  accuracy  the  morning  is  favored,  though  but  slightly.  In 
the  more  strictly  mental  and  in  the  more  complex  activities,  there  is 
a  similar  inclination  to  the  morning  periods  both  in  rate  and  in  accu- 
racy. Adult  students  and  authors  seem  to  think  the  earlier  part  of 
the  day  best  for  their  respective  employments,  but  in  practise  both 
draw  heavily  on  the  night  period,  while  in  the  case  of  females  and 
children  the  morning  maximum  seems  to  be  the  rule.  The  suggested 
morning  efficiency  of  adults  does  not  hold  good,  however,  of  the  first 
moments  after  arising,  where  there  still  appears  an  inertness  com- 
parable to  that  on  the  motor  side,  though  less  evident  and  more 
evanescent. 


NOTE 

There  came  to  my  attention  as  this  paper  was  about  to  issue  from  the 
press,  the  interesting  work  of  J.  A.  Bergstrom  on  '  A  Study  of  Mental  Activity,' 
in  the  Amer.  Jour,  of  Psych,  for  1894.  Only  chief  and  brief  cross-references  can 
be  made.  For  rate  of  movement,  a  simple  test  Avas  used;  for  old  associations, 
classification  of  words,  and  the  reading,  adding  and  multiplication  of  numbers; 
for  new  associations,  learning  number  series  and  nonsense  syllables  and  the  sort- 
ing of  cards. 

In  movement,  J.  A.  B.  made  this  record,  in  number  of  strokes  per  minute, — 
7  A.M.,  262;  8,  272;  10,  278;  12,  267;  2  p.m.,  277;  4,  270;  6,  269;  8,  260;  10, 
260  (p.  258).  A  subject  of  Mosso's  made  this  record  at  8,  10  and  12  a.m., — 260, 
268,  268   (p.  261 — cf.  p.  17  above). 

In  memory  of  nonsense  syllables,  E.  C.  S.  progressively  loses  ability  during 
the  day  (p.  249)  ;  while  J.  A.  B.  is  best  at  8  a.m.,  and  worst  at  noon  and  6  p.m. 
(p.  256).  In  old  associations  (sorting  cards),  3  subjects  diminish  in  ability 
from  morning  to  night,  1  increases,  1  is  best  in  afternoon  and  worst  at  night 
and  1  is  the  opposite  (p.  249)  ;  J.  A.  B.  tends  to  follow  his  movement  course, 
but  the  maximum  is  at  6  p.m  ( p.  258 ) .  For  the  other  associational  tests, 
J.  B.  A.  found  a  uniform  curve:  low  ability  at  8  a.m.,  increasing  to  10,  decreas- 
ing to  12,  increasing  to  2  (same  as  10),  then  a  slight  decline  to  6  p.m.  (p.  256 
— cf.  p.  53). 

Some  of  his  more  general  conclusions  follow. 

No  necessary  correspondence  between  pulse  and  mental  rate  (p.  260). 

"  Heerwagen  sent  out  the  following :  What  part  of  the  day  do  you  find 
mental  work  easiest?  182  said  the  morning,  133  the  evening,  6  the  afternoon, 
43  noticed  no  difference,  while  28  found  it  easy  at  all  times.  Professor  E. 
Barnes,  in  a  study  of  the  intellectual  habits  of  Cornell  students,  received  in 
reply  to  the  same  question,  66  votes  for  morning,  6  for  afternoon  and  39  for 
evening.  The  average  student,  he  says,  begins  work  at  8,  but  is  in  doubtful  con- 
dition, is  best  at  9  and  at  10  is  still  in  good  condition,  at  11  is  tired,  and  is  at 
his  worst  at  12.  He  works  from  3  to  5  p.m.,  but  in  inferior  form;  after  supper, 
he  goes  to  work  at  7  and  reaches  his  best  at  8;  from  9  he  is  not  at  his  best, 
and  retires  at  10:30"   (p.  262— cf.  p.  59). 

"  The  familiar  '  warming  up  '  to  work  is  probably  to  be  explained  in  large 
part  by  these  facts  of  nervous  activity  '  ( summation  phenomena ) .  F€re  notes 
that  reaction  time  does  not  reach  its  greatest  rapidity  till  the  stimulating  in- 
fluence of  light  and  heat  has  operated  for  some  time.  Nocturnal  paralysis  and 
morning  tire  are  explained  as  exaggerated  phenomena  of  this  sort'  (p.  264 — 
cf.  p.  71). 

"  The  daily  mental  rhythm  is  much  influenced  by  habit  ( p.  266 — cf .  p.  74 ) . 
These  habits  ( of  authors ) ,  however  acquired,  evidently  have  great  power  of  dis- 
tracting the  attention  if  they  are  not  satisfied,  and  so  retard  work  "  (p.  267 — cf. 
p.  76). 

No  apparent  effect  of  fatigue  upon  sensory  discrimination  (p.  266 — cf. 
p.  79). 

"  Stimulations  which  would  inhibit  in  normal  conditions,  in  fatigue  produce 
reinforcement.  The  fact  that  reinforcements  of  sensations  and  muscular  move- 
ments are  more  prominent  in  neurasthenic  and  hysterical  persons  seems  to  be 
paralleled  here.  The  greater  excitability  and  sleeplessness  in  fatigue  are  an- 
other illustration"  (p.  263 — cf.  p.  88). 

"  There  is  no  general  type  of  daily  rhythm,  and  individual  differences  of 
the  most  striking  sort  occur"   (p.  262— -cf.  p.  95). 

These  results  and  conclusions  largely  agree  with  my  own. 


70  DIURNAL    COURSE    OF   EFFICIENCY 


D.     CHIEF    CAUSAL    FACTORS    IN    THE    DIURNAL 
EFFICIENCY    CURVE 

The  main  effort  up  to  this  point  has  been  to  bring  together  the 
data  that  appear  to  have  most  direct  bearing  on  the  question  of 
diurnal  rhythms.  It  is  only  after  such  an  assemblage  of  the  facts 
that  a  discussion  of  the  causal  factors  can  profitably  be  begun.  The 
problem  is  of  such  nature  that  it  could  utilize  every  known  psy- 
chological fact,  on  the  one  side,  and  run  into  every  possible  theory, 
on  the  other,  if  its  utmost  reaches  were  sought.  Yet,  there  is  no  ulti- 
mate satisfaction  in  a  purely  factual  description,  correct  to  the  last 
word— there  is  always  the  demand  for  explanation,  or  deeper  facts. 
It  is  to  an  endeavor  to  meet  this  demand  in  some  degree  that  the 
present  section  is  mainly  devoted. 

I.    Night-Day  Rhythm— Sleep  and  Activity 

A  first  approach  to  a  solution  is  made  when  it  is  intimated  that 
the  day-night  process  exhibited  by  nature  is  the  primary  condition 
upon  which  depends  the  daily  broad  human  rhythm  of  sleep  and 
activity.  The  wakeful  period  is  the  only  one  that  has  hitherto  been 
touched  in  this  paper,  but  the  variations  occurring  therein  can  not 
be  explained  without  reverting  to  the  preceding  period  of  inactivity. 

Donaldson^  gives  this  physiological  explanation  of  the  whole  mat- 
ter: "After  recuperative  sleep  the  cells  in  the  nervous  system  are 
full-sized  and  granular,  blood  flows  with  a  medium  pressure  through 
the  nerve  centers;  slight  stimuli  elicit  a  ready  response  and  there 
are  general  sensations  of  well-being  and  vigor.  From  the  beginning 
of  the  day  the  process  of  running  down  goes  on ;  all  the  constant 
stimuli  hasten  it,  meals  retard  it,  drugs  modify  it,  per  their  nature. 
The  night  inactivity  is  due  to  accumulation  of  waste  products  of  the 
day's  activity,  and  sleep  to  cerebral  anemia  caused  by  withdrawal 
of  the  blood  from  the  brain  at  this  period.  He  thus  makes  one  fun- 
damental, long  rhythm— a  gradual  depression  toward  night  and 
recuperation  by  sleep. 

All  sorts  of  things  Lave  been  asserted  about  the  office  of  sleep  in 
the  human  economy,"  and  it  is  obvious  that  it  plays  a  highly  bene- 
ficial part.  Theoretically,  Donaldson's  view  is  most  credible,  but 
experimentally  it  proves  untenable  as  a  general  expression  of  the 

^  Growth  of  the  Brain,  322-323.      1898. 

'  For  the  most  peculiar,  see  Bigelow,   The  Mystery  of  Sleep.      1895. 

71 


72  DIURNAL    COUR.SE    OF    EFFICIENCY 

facts.  Adults  are  probably  not  at  their  best  on  arising  and  fre- 
quently show  highest  abilities  in  the  evening.  Aside  from  possible 
histological  evidence  in  its  favor,  the  strength  of  the  opinion  that 
early-morning  efficiency  is  highest  seems  due  to  the  failure  to  apply 
exact  measurements,  leaving  judgment  to  the  feelings,  which  are 
confessedly  unreliable.  One  can  not  tell  just  how  much  he  is  doing  by 
the  effort  he  seems  to  be  expending,  as  various  sorts  of  delusional  and 
reinforcement  effects  show\  The  early  morning  may  be  accompanied 
by  a  not  unpleasant  ennui,  like  that  of  a  convalescent,  which  would 
not  at  all  suggest  the  idea  of  inefficiency,  while  the  afternoon  is  often 
accompanied,  for  many,  by  positively  disagreeable  feelings  of  weari- 
ness, which  emphatically  lead  to  the  idea  of  simultaneous  inefficiency. 
Inefficiency  results  from  weariness,  but  the  amount  tends  to  be  over- 
estimated in  our  minds  while  the  inefficiency  of  the  morning  tends 
to  be  relatively  underestimated. 

The  presence  of  inefficiency  after  sleep  is  shown  not  only  in  the 
foregoing  pages,  but  was  also  found  by  Roemer,'  experimenting  on 
this  matter  directly.  He  sought  to  determine  psychic  efficiency  (1) 
after  normal  sleep  and  (2)  after  curtailment  of  the  normal  period  of 
sleep  at  the  morning  and  night  ends.  His  tests  were  memory  of 
figures,  addition,  controlled  reaction-time  and  association.  His  re- 
sults are  not  given  tabularly  but  stated  thus: 

(a)  The  condition  shortly  after  arising  from  normal  sleep  is  one 
of  more  or  less  weariness  {Miidigheit) . 

(6)  Cut  off  sleep  at  the  night  end,  and  little  alteration  occurs  be- 
cause the  loss  is  made  up  by  deeper  subsequent  sleep. 

(c)  Cut  off  sleep  at  the  morning  end,  and  fatigue  (Ermiidung) 
results. 

Later*  he  essayed  to  ascertain  the  effect  of  afternoon  sleep  on 
performance  and  found — by  tests  of  memory  and  addition — that  a 
male,  '  normally  feeling  languid  after  lunch, '  showed  marked  increase 
of  ability  after  a  nap;  while  a  female,  not  subject  to  such  languor, 
showed  the  opposite  effect. 

From  these  experiments  he  concludes  that  Mildigkeit  is  a  brain 
condition,  while  Ermiidung  is  due  to  tissue  consumption  in  the  organ- 
ism. As  the  connotation  of  'fatigue'  has  been  narrowed  since  'weari- 
ness' has  received  acceptation,  so  it  should  be  still  further  restricted 
by  another  characterization  representing  this  morning  condition, 
which  may  well  be  termed  'inertness.'    Tliis  carried-over  sleep  effect 

1 '  Ueber  einige  Beziehungen  zwischen  Schlaf  und  geistigen  Thatigkeiten,' 
Vortrag,  Cong,  fiir  Psych.      1896. 

2 '  Experimental  Studien  iiber  den  Xachmittagssclilaf,'  All  gem.  Zeitschrift 
f.  Psychiat.,  53:  860-803.      1897. 


CAUSAL    FACTOBS    IN    DIURNAL    EFFICIENCY    CURVE 


73 


seems  something  different  from  the  weariness  and  fatigne  that  result 
from  the  day's  activity.  This  matter  will  be  taken  np  again  soon. 
In  respect  to  Roemer's  second  investigation,  regarding  afternoon 
sleep,  the  alleviation  of  the  condition  of  fatigue  in  one  subject,  and 
the  initiation  of  inertness  in  the  other,  may  be  sufficient  to  explain 
the  results. 

Various  researches  on  sleep  have  established  the  fact  that  by  far 
the  soundest  portion  during  the  night  is  that  of  the  first  three  hours. 
For  instance,  this  was  found  by  Michelson'  to  be  true  for  four  sub- 
jects. The  writer  has  chosen  from  his  plotted  curves  one  which 
would  be  more  typical  of  their  average  tendency,  if  it  reached  a 
maximum  at  the  second  hour  instead  of  the  first ;  but  it  was  selected 
rather  with  a  view  to  illustrating  a  conception  of  how  early  morning 
inefficiency  arises  and  how  the  start  of  the  fundamental  diurnal  curve 
is  determined. 


PA 

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---- 

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-5 

HO 
-15 
-10 
■25 

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V 

Fig.   5.      The   Hourly   Depth   of   Sleep — after   Michelson. 

If  this  curve  of  degree  of  unconsciousness  be  conceived  as  repre- 
senting a  person's  degree  of  physical  inefficiency,  it  will  be  noted 
that  normal  ability,  designated  by  the  base  line,  is  not  reached  on 
arising,  but  that  the  curve  is  slowly  approaching  it  at  this  point  and 
at  the  same  general  rate  would  reach  it  about  10  or  11  a.m.  The  facts 
already  cited  lead  us  to  suppose  that  this  is  exactly  what  happens. 
Sleep  imposes  an  inertness,  more  or  less  pronounced,  whose  influence 
but  gradually  passes  away  in  adults  on  arising.  This  first  condi- 
tion represents,  as  it  were,  an  adaptation  of  the  organism  to  nocturnal 

»  '  Ueber  die  Tiefe  des  Schlafes,'  Psycli.  Arheiten,  2 :  1  Heft. 


74  DIURNAL    COURSE    OF    EFFICIENCY 

inactivity,  to  remove  which  some  little  time  is  required  after  awaken- 
ing to  the  exigencies  of  active  life. 

As  the  period  prior  to  awakening  can  be  thought  of  as  one  of 
dwindling  negative  internal  stimulation— of  passing  sleep  effect- 
so  may  the  subsequent  period  be  considered  as  one  of  increasing  posi- 
tive auto-stimulation— of  growing  awakeness.  It  would  not  follow 
—though  it  would  be  suggested— that  because  sleep  exhibits  different 
levels  of  consciousness,  therefore  wakeful  life  should  do  the  same,  but 
the  fact  is  experienced  by  all  and  needs  no  proof.  The  inner  tend- 
ency to  '  warming  up, '  due  partly  to  habit,  is  amplified  by  the  cumu- 
lative effect  that  succeeding  stimuli  have  on  us— an  eft'ect  which  is 
seen  in  its  simplest  and  most  definite  form  in  the  well-established 
fact  of  'summation  of  stimuli,'  demonstrated  by  physiological  ex- 
periments on  muscle  and  nerve.  The  physiological  discharges  take 
place  more  and  more  readily  during  the  morning,  till  a  certain  level 
is  reached  for  the  individual,  or  accidental  causes  of  depression  inter- 
fere. In  short,  it  may  be  said  that  the  night's  general  habit  of  in- 
activity and  the  night's  immediate  sleep  effect  are  instrumental  in 
imposing  on  us  a  morning  period  of  physical  inertness,  more  or  less 
reflected  in  the  mental  life ;  and  that  the  general  habit  of  day  activity 
together  with  its  frequently  repeated  stimulations  tends  increasingly 
to  lead  us  to  higher  levels  of  efficiency — up  to  a  certain  limit. 

This  tendency  meets  with  modifying  and  restricting  influences, 
however,  the  relative  force  of  which  determines  the  actual  form  of 
the  efficiency  curve  for  each  individual.  When  one  reviews  some 
of  the  things  which  can  profoundly  aft'ect  the  human  organism  in  its 
functionings,  the  first  thought  is  that  there  could  be  no  great  part 
of  the  individuals  in  any  group  who  would  probably  conform  to  any 
one  type  of  curve.  This  seems  to  be  true  when  any  great  refinement 
of  it  is  undertaken.  But  in  the  broad  sweeps  suggested,  there  is  still 
chance  of  coming  to  ground  common  to  many,  as  was  shown  in  the 
previous  paragraph.  Personal  habits  are  accidental  as  far  as  a 
common  curve  is  concerned,  and  must  therefore  be  disturbing  ele- 
ments. They  can  not  profitably  be  treated  apart  from  the  actual 
cases,  save  in  a  general  way,  but  the  universal  custom  of  eating  offers 
something  more  substantial  for  discussion. 

II.     Habits,  Meals,  etc. 

The  effect  of  habit  was  used  as  a  partial  basis  for  the  preceding 
statements.  It  is  also  applicable  when  the  habit  is  more  special  and 
is  voluntarily  assumed.  If  a  person,  with  afternoon  maximum 
strength,  were  consistently  and  long  to  exercise  only  in  the  morning, 


CAUSAL   FACTORS   IN    DIURNAL    EFFICIENCY   CURVE 


75 


his  curve  would  very  probably  be  altered  accordingly.  Students  are 
proportionately  much  better  at  night  in  mental  labor  than  people 
unaccustomed  to  study  then.  Writers  who  have  set  the  morning  as 
the  time  for  composition  in  spite  of  feelings  to  the  contrary,  come 
eventually  to  consider  it  their  best  period  and  work  then  with  the 
least  friction.  Illustrations  might  be  multiplied,  but  it  seems  enough 
to  say  that,  in  general,  just  as  physiologically  there  occur  periodic 
hints  of  meal-time— even  to  the  point  of  faintness  and  sickness  with 
some  people,  if  the  customary  time  be  passed  by  so  much  as  an  hour 
— so  it  is  probable  that  in  all  cases  of  habituation  similar  phenomena 
occur  which,  with  their  mental  accompaniments,  become  the  sources 
of  secondary  fluctuations  in  the  individual  curves. 

"The  noonday  dinner  gives  one  both  a  bad  stomach  and  a  bad 
conscience,  and  results  eventually  in  an  empty  head."  So  says 
O'Shea,^  after  much  attention  to  the  food  question  in  relation  to 
mental  economy.  Roemer-  experimented  eight  days  on  the  effect  of 
food,  using  as  tests  half  hours  of  addition  at  9, 10, 11  a.m.  and  12  m. — 
four  days  with  breakfast  and  four  days  without,  alternately.  Table 
XXIX.  shows,  first,  the  absolute  number  of  additions  and,  second, 
the  reduction  of  the  same  to  percentage  of  the  first  hour's  per- 
formance. 

Table  XXIX.     Effect  of  Loss  op  Meats  on  Adding  Ability — After  Roemee. 


Number  added. 

Per  cent,  of  first  hour. 


Without  food. 
10:00.     11:00. 


6,741    5,856    5,707    5,990 
100         87         84         90 


With  food. 
9  A.M.     10:00.     11:00.     12:00. 


;  8,695   8,453  7,906   7,831 
100        97        91        89.5 


The  series  of  experiments  was  too  short  to  prove  anything,  but 
the  results,  in  the  light  of  the  noon  records,  scarcely  seem  to  suggest 
his  conclusion  of  a  beneficial  food  influence  so  much  as  that  the  rela- 
tively bad  records  at  10  and  11,  of  the  days  without  food,  were 
dependent  on  the  disturbance  consequent  upon  the  irregularity.  It 
is  but  fair  to  Roemer  to  say  that  he  admits  this  as  a  possible  factor, 
but  he  fails  to  give  it  sufficient  weight. 

Kraepelin'  holds  a  similar  view  as  to  food  effect:  "The  psychic 
disposition  of  the  individual  shows  in  general  during  the  day  quite 
definite  changes — an  increase  of  performance  ability  till  about  noon, 
a  quick  fall  after  lunch,  a  new  increase  in  late  afternoon  and  a  final 

^Op.  cit. 

'  Weggandt,  '  Roemer's  Versuche  iiber  Nahrungsaufnahme  u.  geistige  Leist- 
ungsfahigkeit,'  Psych.  Arbeiten,  2:   695-706.     1899. 

^ '  Ueber  Ermiidungsmessungen,'  Archiv  f.  die  gesamte  Psych.,  1:  9-30. 
1903. 


76  DIURNAL    COURSE    OF    EFFICIENCY 

evening  fatigue.  Regeneration  is  accomplished  by  food  on  the  one 
hand  and  by  sleep  on  the  other."  He  later  alters  this;  namely,  he 
finds  an  increase,  both  phj^sical  and  mental,  after  each  meal.  This 
is  the  source  to  him  of  the  diurnal  variations. 

That  meals  have  an  influence  is  true,  but  that  it  consists  in  an 
immediate  tendency  to  increasing  ability  is  not  clearly  seen.  Finzi,^ 
for  one,  says  just  the  opposite— that  they  reduce  the  speed  of  all 
functions.  Many,  if  not  most,  experimenters  on  the  effects  of  dif- 
ferent agencies  (alcohol,  tobacco,  food  and  foodstuffs,  drugs,  sleep, 
etc.)  fall  into  what  seems  to  be  a  serious  error,  already  mentioned. 
That  is,  the  fact  is  overlooked  that  elimination  of  customary  influ- 
ences affects  the  organism  as  radically  as  does  its  subjection  to  posi- 
tive stimuli.  The  immediate  effect  of  breaking  a  habit  is  apt  to  be 
detrimental,  whatever  the  habit  may  be.  This,  it  may  be  said  in 
passing,  is  one  of  the  most  subtle — and  vitiating — elements  of  all 
experimentation.  When  a  smoker  quits  that  habit  for  a  few  experi- 
ments, two  causes  figure  in  the  result ;  one  the  change  of  a  particular 
condition— which  is  the  one  aimed  at— and  one  the  alteration  of  an 
habitual  condition— which  is  the  one  so  frequently  ignored.  There 
is  reaction  to  the  one  as  to  the  other,  physiologically  and  psycholog- 
ically. The  writer  found  in  a  five  days'  course  of  fasting,  by  both 
objective  tests  and  subjective  feelings,  that  the  greatest  disturb- 
ance, mentally  and  physically,  occurred  on  the  first  and  second  days 
— the  latter  particularly — after  which  gnawings,  headaches  and 
nausea  began  noticeably  to  subside  and  the  abnormal  condition 
tended  appreciably  to  become  normal  to  the  end  of  the  course.  Data 
obtained  only  from  those  first  few  days  would  have  been  quite  mis- 
leading. 

Some  good  evidence  on  the  persistence  of  habitual  periodicity  in 
activity  is  contained  in  an  article  by  Patrick  and  Gilbert  on  the 
'Effect  of  the  Loss  of  Sleep,'-  though  the  authors  do  not  utilize  the 
material  for  this  purpose.  Two  subjects,  A.  G.  S.  and  G.  N.  B.,  were 
kept  awake  72  hours  and  various  tests  were  given  them  every  6  hours. 
On  successive  days,  the  ivorst  records  were  made  at  the  following 
hours,  showing  the  subjective  disturbance  to  be  greatest  at  the  periods 
ordinarily  devoted  to  inactivity— to  sleep.  The  first  day,  being  un- 
affected, is  omitted. 

1.  Adding. 

A.  G.  S.— 3  A.M.,  3  A.M.,  9  P.M.  (last  test  taken). 
E.  N.  B.— 3  A.M.,  3  A.M.,  9  P.M.  (last). 

^Normalen  Schivankungcn  der  Seelc7ithdtigkeiten,  Reprint,  p.   14.     1900. 
^Univ.  of  loica  Studies  in  Psych.,  1:   40-61.      1897. 


CAUSAL    FACTORS    IN    DIVRXAL    EFFICIENCY    CURVE  77 

2.  Hearing. 

A.  G.  S.— 3  A.M.,  3  A.M.  (none  after  3  p.m.). 
E.  N.  B.— 3  A.M.,  9  P.M.,  3  P.M.  and  9  p.m.  (last). 

3.  Discrimination  of  letters. 

A.  G.  S.— 3  A.M.,  3  A.M.,  3  A.M.  and  9  p.m.  (last). 

E.  N.  B.— 3  A.M.  and  9  p.m.  to  9  a.m.,  9  p.m.  to  9  a.m.  and  9  p.m. 

4.  Strength. 

A.  G.  S.— 3  A.M.,  3  A.M.,  9  a.m.  (none  taken  at  3  a.m.). 
E.  N.  B.— 3  P.M.,  9  A.M.,  9  p.m.  (last). 

5.  Memory. 

A.  G.  S.— 3  A.M.,  3  A.M.  and  9  p.m.  to  3  a.m.,  9  p.m.  (last). 
E.  N.  B.— 3  A.M.  and  9  p.m.,  3  p.m.,  9  p.m.  (last). 

The  times  of  the  best  records  point  .just  as  strongly  in  the  same 
direction.  These  results,  aside  from  the  effects  of  loss  of  sleep,  show 
the  recurrent  nature  of  an  established  habit  and  how  important 
must  be  its  influence  in  every  individual  curve. 

By  all  my  subjects,  the  heaviest  meal  of  the  day  was  eaten  about 
6  or  7  P.M. ;  hence  the  fourth  period  should  show  the  best  work,  if 
meals  alone  cause  the  differences.  Subjects  I.  and  A  ate  very  light 
lunches,  yet  the  5  p.m.  period  is  the  best,  as  to  strength  at  least, 
Lombard^  seems  to  be  right  when  he  says,  "the  temporary  influence 
caused  by  a  meal  can  not  long  delay  the  decline  nor  can  it  hasten 
the  increase  of  strength  which  is  caused  by  the  diurnal  alterations 
of  the  power."  Eest  and  social  elements  are  also  involved  in  the 
nature,  amount  and  permanence  of  the  change  in  ability  wrought 
by  the  meal  interval. 

III.    Fatigue  and  Feelings  of  Fatigue 

Granted  that  periodical  changes  in  individual  curves  of  efficiency 
do  exist  for  time  of  day,  it  is  evident  that  no  credible  theory  of  their 
cause  could  be  constructed  without  reference  to  those  effects,  to 
which  all  are  subject,  that  have  been  treated  usually  under  the  head 
of  '  fatigue. ' 

Chronologically,  the  study  of  diurnal  variations  in  ability  orig- 
inated from  an  interest  in  the  problem  of  fatigue.  One  can  not  look 
over  the  literature  of  the  subject  without  noting  that  the  experi- 
ments on  motor  power,  following  the  introduction  of  the  Mosso  ergo- 
graph  in  1890,  were  largely  influential  in  turning  attention  to  the 
measurement  of  human  functions,  mental  even  more  than  physical. 
Some  earlier  work  had  been  done  by  Sikorsky  (79),  Hodge  ('87), 

^ '  Some  Influences  affecting  Voluntary  Work,'  op.  cit.,  p.  30. 
6 


78  DIURNAL    COURSE    OF   EFFICIENCY 

Galton  ('88),  Oehrn  ('89),  and  a  few  others,  but  did  not  attract 
much  attention.  In  Germany,  an  immense  impetus  was  given  to 
such  investigations  by  pedagogical  needs  and,  indeed,  the  whole  prob- 
lem of  periodicity  and  fatigue  may  be  said  to  have  taken  its  rise 
from  this  relation  to  school  life,  and  its  solution  to  have  its  most 
valuable  application  there.  Therefore  the  treatment  of  this  section 
will  be  rather  extensive,  though  it  will  be  impracticable  even  to  refer 
to  the  mass  of  original  work  in  this  direction  undertaken  since  1890. 

1.  Muscular'  Fatigue 
Fatigue  tests  here  are,  in  one  aspect,  strength  tests,  and,  there- 
fore, have  already  received  some  mention.  By  far  the  greater 
amount  of  the  work  in  this  immediate  connection  has  been  taken 
up  with  a  view  to  determining  the  location  of  the  seat  of  fatigue 
— whether  it  is  central,  neural,  muscular,  etc.  Ultimately  these 
considerations  must  be  utilized  in  any  thoroughgoing  treatment 
of  the  diurnal  problem,  but  the  same  can  as  truthfully  be  said 
of  any  group  of  facts  concerning  the  living  being,  if  the  question 
be  in  no  wise  limited.  So  far,  then,  as  these  experiments  have 
been  carried  out  without  reference  to  time  of  day  they  must  be 
ruled  out,  but  so  far  as  they  have  been  used  as  mental  measures, 
they  will  be  discussed  immediately  below. 

2.    Mental  Fatigue 

1.  Measured  iy  Motor  Inefficiency. — One  primary  question, 
whether  decrease  in  muscular  power  is  a  trustworthy  sign  of 
fatigue  in  mental  function  or  not,  has  sometimes  received  em- 
pirical consideration,  but  cpiite  as  often  an  affirmative  answer  has 
been  assumed  as  true. 

Bolton,^  in  the  course  of  his  theory  of  motor  development, 
says:  "Tests  of  motor  power  may  be  used  as  measurements  of  in- 
telligence or  mental  alertness.  ...  As  substitutes  for  the  old- 
fashioned  methods  of  examination  .  .  .  tests  of  physical  en- 
dowment and  of  general  healthfulness  of  body  seem  to  offer  the 
most  promise.    .    .    ." 

Lukens-  is  authority  for  the  statement  that  Kemsies  with  the 
ergometer  found  distinct  correlation  between  mental  fatigue  and 
lessened  muscular  power  and  that  'the  ergometer  showed  the 
fatigue  in  certain  cases  to  have  continued  several  days'  after 
some  insevere  night  mental  tests."      What  he  found  the  following 

"Motor  Power,'  Am.  Jour,  of  Psych.,  14:   613-031.      1903. 

^ '  The  School  Fatigue  Question  in  Germany,'  Ed.  Rev.,  15.      1898. 

*  Bettman  ( see  Bibliog.,  Part  E )  also  says  that,  though  no  permanent 
injury  to  ability  resulted  from  night  tests  in  adding,  '  a  very  strong  fatigue 
affected  the  disposition  for  several  days  following.' 


CAUSAL    FACTORS    IN    DIURNAL    EFFICIENCY    CURVE  79 

mornings  was  probably  not  residual  fatigue  so  much  as  the  nor- 
mal condition  of  inertness.  He  and  others  have  arranged  cur- 
ricula in  accordance  with  the  results  of  such  ergographic  tests 
after  recitations  in  the  various  branches. 

Christopher  and  Smedley,  in  the  articles  noted  above,  make 
the  assmnption  of  such  a  direct  relation  between  mental  fatigue 
and  motor  force,  the  former  advising  that  'physical  condition 
should  be  a  factor  in  grading,  especially  for  entrance  to  first 
grade,'  while  Smedley  says  that  'certain  parts  of  the  school  day, 
when  pupils  on  the  average  have  a  higher  storage  of  energy  than 
at  others,  should  be  utilized  for  the  highest  forms  of  educational 
work.'  The  one  assumes  that  mental  fatigue  is  present  when 
the  ergographic  records  are  low;  the  other,  that  it  is  absent  when 
they  are  high. 

Ellis  and  Shipe^  assume  throughout  their  trials  that  fatigue 
is  present  in  the  afternoon,  and  hence  when  the  tests  fail  to  show 
it,  the  tests  are  voted  valueless.  They  took  reaction-time  and 
ergographic  tests  on  six  subjects  for  five  days,  twice  a  day  ( 1 
A.M.  and  12:30  p.m.)  and  found  that  "these  tests  seem  to  show 
that  the  students  (college)  w^ere  as  fresh  at  noon  as  at  the  be- 
ginning of  the  day.  Their  appearance  and  feelings  belied  their 
results"  (p.  234).  Such  acceptance  of  the  emotional  evidence 
of  fatigue  is  an  easy  but  serious  mistake  to  make.  Various 
w'riters^  have  pointed  out  the  need  of  observing  the  distinction 
between  fatigue  proper  and  the  feelings  of  fatigue. 

Where  my  own  subjects  not^d  mental  depression  or  even  head- 
ache on  their  records,  the  figures  rarely  failed  to  show  a  high 
grade  of  muscular  performance  at  the  time.  But  the  younger 
the  individual  the  more  prone  he  is  to  follow  his  feelings,  in  the 
quantity  and  quality  of  his  work.  Especially  was  this  noticeable 
among  the  coin-case  workers,  whose  every  (seen)  gape  and  sleepy 
look  was  duly  registered.  Still,  it  is  yet  to  be  proven  that  there 
is  a  causal  connection  between  mental  and  motor  deficiency  such 
that  one  may  be  an  accurate  measure  of  the  other. 

2.  Measured  hy  Sensory  Inefficiency. — Another  conception  is  that 
the  degree  of  insensitivity  of  the  skin  is  a  measure  of  fatigue. 
Griesbach-^  was  the  originator  of  the  esthesiometric  method  of  study- 
ing fatigue  and  performed  many  experiments  with  it.  He  deter- 
mines the  least  distance  on  the  skin  at  which  the  two  points  of  the 

t  'A  Study  of  the  Accuracy  of  Present  Methods  of  Testing  Fatigue,'  Am. 
Jour,  of  Psych.,  14:   232-245.     1903. 

» Cowles,   MacDougall,   Dearborn,   Thorndike,  Kraepelin,  Roemer,  etc. 

'  Eneryetik  und  Hygiene  des  Xervensystems  in  der  Schule,  S.   1-95.      1895. 


80  DIURNAL    COURSE    OF   EFFICIENCY 

instrument,  on  being  gradually  approached  from  a  point  where  they 
are  easily  distinguished,  are  perceived  as  two;  or  the  greatest  dis- 
tance at  which  two  points  are  perceived  as  one,  on  being  gradually 
separated  from  below  the  so-called  threshold.  His  results  were 
thought  remarkably  decisive  and  consistent,  so  much  so  that,  like 
his  followers  Vannod  and  Wagner  with  the  same  instrument,  and  like 
Kemsies  and  others  with  the  ergograph,  he  was  able  to  obtain  a 
fatigue  coefficient  for  each  branch  of  study  and  then  to  assign  each 
to  its  proper  place  in  the  daily  school  routine.  The  only  trouble  is 
that  the  different  results  do  not  accord. 

Griesbach  found  that  the  sensitivity  changes  little  during  the 
day  under  normal  conditions,  but  gradually  decreases  imder  school 
conditions.  He  tested  the  pupils,  professors  and  mechanics  of  a 
school,  on  the  forehead,  nose,  cheek,  underlip,  ball  of  thumb  and  ball 
of  forefinger.  By  averaging  these  six  determinations  he  obtained 
a  very  typical  curve  of  the  changes  in  the  threshold.  The  following 
figures  show  the  resulting  values  in  millimeters. 

Table  XXX.     Esthesiometeb  Tests — Revision  after  Griesbach. 


a 

.a 

a 

A.M. 
reek. 

< 

O 

(-. 

g 

s 

« 

t^ 

s 

00 

>-i 

a>       O 

« 

•^ 

Oh 

w 

'-' 

tf 

M 

« 

2  ZO 

5.8 

1 

8.0 

1 

10.0 

10.8 

1 

7.3 

1 

9.8 

— 

1 

3.5 

1 

2.7 

Griesbach,  therefore,  demands  (1)  no  school  work  in  the  after- 
noon, (2)  later  beginning  in  morning — on  account  of  residual  fatigue 
from  the  previous  day,  (3)  abolishment  of  examinations,  (4)  less 
home  work  and  less  learning  by  heart.  Special  attention  is  called 
to  the  high  afternoon  sensitivity  compared  with  that  of  the  early 
morning — true  both  of  the  work-day  and  the  rest-day  following. 
His  method  has  been  much  tried  and  criticized,  but  only  a  few  of 
the  leading  articles  can  be  referred  to. 

MacDougall,^  after  adverse  criticism  of  other  methods,  says  of 
Griesbach 's  that  it  is  'decidedly  satisfactory';  that  by  it  can  be 
found  the  best  hours  and  days  for  study  and  the  length  of  study 
periods  proper  for  different  ages.  He  produces  no  experimental 
proof  of  his  own. 

Leuba^  attacks  the  method  and  results.  He  tested  three  adult 
male  students  for  fourteen  days,  at  9  a.m.,  11  a.m.,  1  p.m.,  5  p.m.  and 
9  P.M.,  on  cheek  and  thumb,  6,000  judgments  in  all.      He  found 

^  Am.  Jour,  of  Physiol,  19.      1898. 

^'Validity  of  the  Griesbach  Method  of  Determining  Fatigue,'  Psych.  Rev., 
6.     1899. 


CAUSAL   FACTORS    I\    DIURNAL   EFFICIENCY    CURVE 


81 


divergent  results  as  betAveen  cheek  and  thumb  and  as  between  one 
and  two  point  determinations  on  the  thumb  alone,  and  his  results 
were  also  diametrically  opposed  to  those  of  Griesbach,  Vannod  and 
Wagner.  They  showed,  on  the  whole,  a  marked  increase  in  sensi- 
tivity up  to  5  P.M.  and  thence  a  steady  decrease.  The  results  for 
this  group  and  for  the  one  described  below  are  graphically  repre- 
sented in  his  publication,  but  have  been  transmuted  into  figures  by 
the  present  writer,  as  indicated  in  Table  XXXI.  Work  and  rest 
days  are  given  separately.  The  second  series  was  on  six  adult 
female  students,  2,000  judgments,  at  8 :15  a.m.,  10 :15  a.m.,  11 :15  p.m. 
and  1 :15  p.m.  It  gave  similar  results,  diverse  for  forehead  and 
cheek  as  to  the  single  individuals,  but  showing  considerable  con- 
stancy in  the  total  curves.  The  females  also  start  with  a  relatively 
low  sensitivity  and  increase  as  steadily  as  the  males. 


Table   XXXI. 


ESTHESIOilETER    TeSTS  :     THRESHOLD    IN    MM. — ReTISION    AFTEB 

Leuba. 


Male 

9:00  A.M. 

11:00  A.M. 

1:00 

P.M. 

5:00 

P.M. 

9:00  P.M. 

Subjects. 

Work. 

Rest. 

W. 

R. 

W. 

R. 

W. 

R. 

W.       R. 

1 

14.5 

14.0 

15.1 

13.3 

14.5 

13.6 

14.0 

14.1 

14.4    14.6 

2 

15.8 

15.4 

15.2 

15.5 

15.7 

16.2 

14.9 

16.1 

14.8    16.6 

3 

8.0 

8.4 

7.5 

7.2 

7.4 

7.1 

7.1 

6.7 

8.1      7.6 

Average. 

12.8 

12.6 

12.6 

12.0 

12.5 

12.3 

12.0 

12.3 

12.4    12.9 

Female 

8 :  15  A.M. 

10:15  A.M. 

11:15  A.M. 

1:15 

P.M. 

Subjects. 

Forehead 

Cheek. 

F. 

C. 

F. 

c. 

F. 

C. 

1 

16 

22.0 

15 

22.0 

14 

20.5 

14 

20.5 

2 

11 

13.0 

9 

11.0 

11 

15.0 

10 

12.0 

3 

7 

11.0 

6 

11.5 

4 

8.0 

3 

8.8 

4 

12 

21.9 

17 

21.0 

14 

22.0 

13 

22.1 

o 

8 

10.0 

6 

8.8 

7 

8.0 

8 

8.0 

6 

8 

11.0 

5 

11.0 

5 

11.1 

5 

9.0 

Average. 

10.5 

14.8 

9.7 

14.2 

9.2 

14.1 

8.8 

13.4 

Germann^  used  both  one  and  two  points,  noting  the  number  of 
errors  at  the  threshold.  The  experiments  were  made  on  an  adult 
female  student  studying  eight  or  nine  hours  daily;  she  was  tested 
at  about  8 :30  a.m.  and  9 :30  p.m.  ;  2,450  judgments  were  made. 
Table  XXXI.  gives  the  results  of  fourteen  days,  in  each  of  which 
a  pair  of  tests  were  taken. 


Table  XXXII. 

Esthesiometeb 

Records — After 

Germann. 

Errors. 

A.M.  =  P.M. 

A.M.  >  P.M. 

A.M.  <  P.M. 

Total. 
2-point. 
1-point. 

4 
1 
2 

8 
9 
9 

2 

4 
3 

^ '  On  the  Invalidity  of  the  Esthesiometric  Method  as  a  Measurement  of 
Mental  Fatigue,'  Psych.  Rev.,  6.      1899. 


82  DIURNAL    COURSE    OF   EFFICIENCY 

This  means  that  the  percentage  of  erroneous  judgments  in  the 
morning  was  equal  to  that  in  the  evening  on  four  days ;  greater  on 
eight  days ;  less  on  two  days ;  etc.  Plenee  he  concludes  that  "in  at 
least  one  normal  case  the  percentage  of  errors  in  cutaneous  tactile 
discrimination  bears  no  constant  nor  even  relative  correspondence 
to  the  mental  fatigue  experienced  by  the  subject."  This  conclusion 
is  hasty,  as  it  possibly  confuses  fatigue  and  feelings  of  fatigue  and 
fails  to  take  account  of  the  state  of  inertia  which  has  been  emphasized 
as  occurring  early  in  the  morning. 

It  is  suggested,  therefore,  that  the  morning  insensitivity  observed 
by  these  various  experimenters  is  not  at  all  a  symptom  of  technical, 
nor  of  'residual,'  fatigue,  nor  yet  of  subjective  weariness,  but  rather 
of  inert  physical  condition  unconnected  directly  with  any  one  of 
them.  It  is  also  a  mistake  to  assume  that  insensitivity  can  arise 
only  as  a  result  of  fatigue,  and  just  as  much  a  mistake  to  suppose 
that  much  fatigue  is  necessarily  present  in  adults  in  the  afternoon 
or  after  several  hours'  effort.  INIany  other  authors  also  have  demon- 
strated the  unsafeness  of  this  method  for  measuring  mental  fatigue.^ 

3.  3Ieasured  by  Mental  Inefficiency .— A  closer  approach  to  a 
purely  mental  test  of  fatigue  is  found  in  the  reaction-time  or  asso- 
ciation-time method  first  used  by  Cattell."  In  a  course  of  experi- 
ments Avitli  different  sorts  of  stimuli,  reactions  (1,950  in  all)  were 
continued  for  a  whole  day,  from  7 :30  a.m.  to  8  :30  p.m.,  with  short 
intervals  for  eating.  The  results  are  thus  summed  up :  "  The  first 
result  to  be  noted  is  the  very  slight  effects  of  fatigue ;  in  no  case  is 
the  time  lengthened  more  than  a  couple  of  hundredths  of  a  second 
and  the  mean  variation  is  but  little  increased.  "We  reach  the  un- 
expected conclusion  that  the  processes  which  are  most  automatic — 
naming  colors  and  simple  reaction-time  to  sound— are  the  most 
affected  by  fatigue." 

This  method  was  also  employed  by  Roemer  and  by  Ellis  and 
Shipe.'  The  latter  determined  the  reading  time  for  words  of  four 
letters,  in  morning  and  at  noon,  and  state  their  results  in  the  words 
quoted  on  page  79,  above.  In  regard  to  a  second  series  of  various 
tests,  they  say,  "Of  24  perfect  records  reaction-time  was  shorter 
14  times  at  5:30  p.m.;  mean  variation  less  13  times;  total  figures 
added,  more  17  times;  more  added  correctly,  15  times;  more  cubes 
written,  19  times;  more  nonsense  syllables  learned,  15  times.  One 
of  the  best  records  came  just  after  a  long,  hard  examination  (in  the 

» As  Cattell,  Ebbinghaus,  Kraepelin  ('99),  Bolton,  Meiimann,  Kraepelin 
('03). 

»  '  The  Time  taken  up  by  Cerebral  Operations,'  Mind,  12:  44.     1886. 
^  Op.  cit. 


CAUSAL    FACTORS    IN    DIURNAL    EFFICIENCY    CURVE  83 

afternoon)  for  which  the  student,  after  working  and  worrying  all 
the  day  before  had  continued  work  till  2  a.m.  the  night  before." 

Later,  seven  subjects  were  tested  (1)  during  a  w'eek  before  March 
examinations,  (2)  during  the  examination  Aveek  and  (3)  during  the 
one  following.  The  results  practically  agreed  with  those  of  previous 
series,  and  the  authors  report  'the  same  lack  of  agreement  between 
tests  and  the  same  failure  to  indicate  fatigue  in  the  afternoon.'  If 
they  'failed  to  indicate  fatigue'  they  must  have  agreed  somewhat, 
it  w^ould  seem. 

Then  three  subjects  were  used  (four,  three  and  two  days,  re- 
spectively) at  9-10  A.M.  and  5-6  p.m.,  and  results  were  obtained 
'equally  inconsistent  with  each  other  and  with  the  undoubted  facts.' 
These  last  citations  show  the  assumption  in  the  writers'  minds  that 
fatigue  is  the  normal  afternoon  condition  in  the  case  of  all  adult 
students. 

It  appears  from  their  reports  that  the  afternoon  reactions  and 
results  in  general  were  superior  to  those  of  the  morning,  even  though 
the  morning  tests  were  taken  rather  late.  Their  series  of  experi- 
ments were  short  but,  as  far  as  they  go,  confirm  the  views  expressed 
in  the  previous  portions  of  this  paper. 

One  of  the  earliest  tests  to  be  used  was  that  of  'dictation  exer- 
cises,' introduced  by  Sikorsky  in  1879— the  first  attempt  at  objective 
measurement  of  mental  fatigue.  It  was  later  used  by  Oehrn  ('89), 
Hopfner  ( '94),  Friedrich  ( '96),  and  preferred  to  all  others  by  Henri 
and  Binet  ('98).  According  to  its  advocates,  it  is  easily  given  to 
groups,  easily  cheeked  up,  easy  to  understand,  has  no  practise  effect, 
and  the  different  characters  of  the  errors  show  the  different  types 
of  fatigue  (as  for  arithmetic,  gymnastics,  etc.).  Only  those  of 
Sikorsky  and  Friedrich  off'er  direct  evidence  on  the  problem  in  hand. 

Sikorsky,  according  to  Binet, ^  gave  500  dictations  to  six  classes, 
the  members  ranging  in  age  from  nine  to  sixteen  years,  at  9  a.m.  and 
3  P.M.,  before  and  after  the  school  session.  The  number  of  errors 
made  by  each  class  is  given  in  the  following  table.^  Binet  classified 
these  into  phonetic  (omissions  and  substitutions  of  letters),  graphic 
(in  written  form,  etc.),  psychological  (omissions  or  substitutions  of 
words),  indeterminate  (all  others).  These  are  also  shown  in  the 
table  in  per  cents.^ 

^La  Fatigue  Intellectuelle,  288.      1898. 

^  The  figures  are  evidently  percentages  of  something :  Binet  does  not  say 
what. 

^Neither  of  the  revised  columns  totals  100  per  cent.:  Binet  does  not  say 
why. 


84 


DIURNAL    COURSE    OF   EFFICIENCY 


Table   XXXIII.     Fatigue — ^Measured   by   Dictation   Exercises. 


Binet,  after  Sikorsky. 

Binet,  revision  after  Sikorsky. 

No;  of  Class. 

9  A.M. 

3  P.M. 

Per  Cent. 
Diflferenee. 

Kind  of  Error. 

9  A.M. 

3  P.M. 

Class  1 
"     2 
"     3 
"    4 
"     5 
"    6 

123.5 
121.5 
72.4 
66.5 
61.4 
45.7 

156.7 

145.3 

102.8 

94.2 

81.0 

80.0 

+  33.2 

+  23.8 
+  30.4 
+  27.7 
+  19.6 
+  34.3 

Phonetic. 
Graphic. 
Psychic. 
Indeterminate. 

62.6  % 
8.9  % 
4.5  % 
6.0  % 

77.3  % 

11.3% 

8.9  % 

11.9  % 

This  table  interprets  itself.  The  differences  in  efficiency  are  seen 
to  be  very  large,  uniformly  so,  and  can  leave  no  doubt  as  to  the  cor- 
rect inference.  But  still  greater  differences  were  found  by  Friedrich 
with  a  class  of  51,  averaging  ten  years  of  age. 


Table  XXXIV. 


Fatigue — Per  Errors  in  Dictations — Binet,  after 
Friedrich. 


t."  . 

c  . 

tTto 

u    , 

3 

u 

tT  . 

u  . 

4) 

s  a 

s  a 

s  a 

3  a 

s  a 

O 

W-3 

3  a 

3  i^' 

S 

K-l 

o_o 

o  o 

tS-2 

o  o 

WT3 

w-S 

W 

o 

to  ^ 

^2 

n  V 

_  =3 

_  « 

'O   QJ 

1^ 

"S  °* 

ti  0/ 

t3  V 

t2 

1^ 

CO   S 

II 

II 

Go 

m 

<* 

^^ 

-^o 

<« 

<<r-, 

-"l^ 

« 

-^ 

<'-' 

<-o 

45 

70 

123 

158 

112 

166 

184 

65 

152 

109^ 

185 

These  figures  serve  to  show  the  effect  of  recreation  periods,  as 
well  as  the  gradual  increase  of  fatigue. 

The  Ebbinghaus  'method  of  combinations'  was  used  by  its  author 
in  1897,^  in  extensive  tests  on  school  children  of  five  grades,  before 
the  first  hour  and  after  each  of  the  next  five.  Passages  with  words 
skipped  were  given  to  the  pupils  to  fill  in  and  the  results  were  scored 
in  number  of  spaces  filled  and  number  of  errors  made.  He  found, 
with  few  exceptions  in  any  grade,  a  gradual  increase  of  errors  till 
noon,  a  recovery,  then  another  drop  in  ability.  The  youngest  ones 
fatigue  most  rapidly,  as  shown  by  the  number  of  mistakes.  This 
seems  to  be  the  typical  curve  for  children  under  work  conditions. 

Mathematics,  considered  hardest  of  primary  studies,  has  naturally 
been  much  employed  as  a  fatigue  test.  Addition  or  multiplication 
was  used  for  more  or  less  extensive  diurnal  tests  by  Oehrn  ('89), 
Burgerstein  ('91),  Laser  ('94),  Schulze  ('95),  Amberg  ('96),  Fried- 
rich ('96),  Kemsies  ('96),  Ebbinghaus  ('97),  Rivers  and  Kraepelin 
('97),  Roemer  ('99),  Thorndike  ('00),  Kraepelin  ('03),  Ellis  and 
Skipe  ('03)  and  others.     The  results  as  a  Avhole  tend  to  show  a  de- 

' '  Une  Nouvelle  Methode  d' Appreciation  des  Capacite  Intellectuelle,'  Rev. 
Scient.,  4  e  S,  8:  424-430.      1897. 


CAUSAL    FACTORS    IN    DIURNAL    EFFICIENCY    CURVE  85 

crease  of  ability  in  children  at  the  periods  just  mentioned.  Thorn- 
dike's  results^  present  a  striking-  contrast  to  those  of  the  majority, 
as  to  both  adult  and  child  students,  and  for  that  reason  will  be  given 
more  attention.  His  chief  object  was  to  test  ability  to  do  mental 
work  before  and  after  periods  of  hard  mental  exercise.  His  study 
comprises  four  separate  articles. 

His  first  article  deals  with  mental  fatigue  in  adults.  First,  men- 
tal multiplication  of  numbers  of  several  places  was  used  as  a  test 
on  three  subjects  for  four  days,  two  trials  in  the  morning,  and  two 
at  night  after  from  seven  to  twelve  hours'  work.  The  results  re- 
ferred to  the  night  period  were :  for  subject  I.,  greater  speed,  less 
accuracy;  for  subject  II.,  greater  speed,  greater  accuracy;  for  sub- 
ject III.,  greater  speed,  less  accuracy.  "In  all  cases  feelings  of 
fatigue  were  reported  at  the  start  of  the  later  experiments." 

Next,  addition  was  used — twenty  numbers  of  five  figures  each — 
with  two  subjects.  They  both  did  better  before  the  day's  work. 
These  results  are  based  on  about  ten  before- work  and  ten  after- work 
trials,  but  nineteen  different  days  are  employed.  This  looks  like 
another  case  of  the  kind  already  frequently  mentioned,  in  which 
every  period  concerned  is  not  represented  in  each  day's  records  used 
in  the  results. 

Then  he  investigates  the  influence  of  mental  work  of  a  particular 
sort  on  ability  to  do  the  same  sort  of  work.  On  the  whole,  there 
was  improvement  in  rate  and  accuracy  at  the  second  period.  He 
concludes  that  incompetency  does  not  come  in  proportion  to  the  work 
done.  "The  decrease  in  energy  does  not  have  enough  influence  to 
outweigh  the  influence  of  practise.  There  is  no  pure  feeling  of 
general  mental  incompetency."  The  feelings  of  fatigue,  as  far  as 
present,  were  not  measures  of  ability.  Confusion  exists  in  experi- 
mental investigations  between  lack  of  desire  and  ability  to  do  work. 

His  second  article  treats  of  mental  fatigue  in  school  children. 
First,  multiplication  was  employed  with  750  Scranton  and  Cleveland 
school  children,  375  being  tested  before  the  morning  session  and  375 
at  the  end  of  the  afternoon  session.  It  was  found  that  the  later 
students  did  99.3  per  cent,  as  much  work  as  the  earlier ;  made  103.9 
per  cent,  as  many  mistakes ;  and  had  114  per  cent,  as  many  bad  papers. 
Other  tests  in  spelling  and  memory  showed  little  or  no  diminution  in 
ability  in  the  afternoon.  It  is  seen  that  there  is  here  some  agree- 
ment with  the  results  of  Rice's  examinations  of  children.  Of  the 
child's  ability  to  do  mental  work  after  a  half  or  whole  scJiool  day, 
Thorndike  says,  however,  that  'he  is  just  exactly  as  able,'  and  that 
boredom  is  accountable  for  95  per  cent,  of  the  apparent  fatigue  in 
'Mental  Fatigue/  Psych.  Rev.,  7:   466-482,  547-579.      1900. 


86  DIURNAL    COUKSE    OF   EFFICIENCY 

schools  during  the  day,  while  good  teaching  is  the  cure.  His  peda- 
gogical inferences  should  be  read  in  their  entirety  to  get  the  full 
force  of  his  contention.  His  conclusions  seem  to  the  present  writer 
to  be  in  the  right  direction  but  rather  too  extreme. 

The  third  article  deals  with  fatigue  of  special  functions  in  adults 
—marking  out  words  that  contained  the  letters  e  and  t;  estimating 
small  areas  for  several  hours;  memorizing  series  of  numbers;  cor- 
recting examination  papers;  assorting  catalogue  cards.  He  finds 
little  fatigue  evidenced  by  the  single  results,  but  they  give  one  a 
somewhat  different  impression  when  considered  as  a  ivliole.  One 
thing  is  obvious,  namely,  the  quantity  of  the  work  is  much  more 
likely  to  be  sustained  than  the  quality.  This  appeared  also  in  the 
first  set  of  experiments  and  is  quite  in  harmony  with  the  outcome 
of  my  own  experimentation.  It  is  possible  that  irregularity  and 
inaccuracy  of  functioning  are  better,  because  more  refined,  indica- 
tions of  fatigue  than  diminished  quantity,  though  actually  the  two 
groups  of  phenomena  are  not  to  be  separated. 

He  takes  up  the  question,  in  the  fourth  paper,  as  to  Avhether 
physical  fatigue  is  a  legitimate  measure  of  mental  fatigue,  and  con- 
cludes that  it  is  not.  Other  data  in  this  direction  were  adduced 
above. 

The  ground  covered  by  Thorndike's  work  was  extensive,  though 
the  series  of  tests  were  often  short ;  there  will  perhaps  be  general 
agreement  with  his  conclusion  that,  judging  from  the  evidence  ad- 
duced, the  amount  of  late-day  inefficiency,  due  to  fatigue,  is  less 
than  is  usually  assumed  and  than  one  might  expect  by  consulting 
one's  feeling  only. 

Memory  and  association  in  various  forms  have  been  favorite 
methods  for  determining  mental  fatigue;  figures,  nonsense  syllables, 
words,  objects,  forms,  colors,  etc.,  have  been  used  as  materials  for 
the  tests.  It  is  undesirable  to  attempt  expression  of  the  results  of 
all  these  investigations,  and  the  same  may  be  said  of  the  outcome  of 
a  variety  of  minor  forms  of  fatigue  tests.  There  are  few  authors 
worthy  of  note  who  do  not  accept  the  idea  that  '  fatigue '  is  present  in 
school  children  before  the  end  of  both  day  sessions,  and  that  recesses, 
diversions,  etc.,  produce  marked  improvement  of  ability. 

Schuytens^  is  one  of  these  few.  With  a  class  of  boys  and  one  of 
girls,  about  eleven  years  old,  he  found  a  great  inferiority  of  afternoon 
work  in  memory  when  the  first  test  w^as  given  in  the  morning,  but 
just  the  opposite  Avhen  the  first  was  given  in  the  afternoon  and  the 
second  the   following  morning.      His  figures  give  percentages   of 

^ '  Sur  les  Methodes  de  Mensuration  de  la  Fatigue  chez  les  Ecoliers/ 
Archives  de  Psych.,  2:  321.      1903. 


CAUSAL    FACTORS    IN    DIURNAL    EFFICIEXCY    CURVE  87 

efBciency  as  follows:  (1)  girls,  62.6  a.m.,  55.1  p.m.;  boys,  57.9  a.m., 
35.0  p.m.  (2)  girls,  77.5  p.m.,  69.6  a.m.;  boys,  64.0  p.m.,  58.1  a.m. 
He  concludes  that  the  first  experiment  on  children  is  ahvaj's  the 
best  and  must  be  eliminated  before  results  are  comparable,  and  that 
this  is  due  to  fluctuations  of  interest  and  not  to  afternoon  fatigue. 
The  pedagogical  suggestion  here  is  quite  similar  to  that  of  Thorn- 
dike  above. 

Opinion  still  remains  rather  diverse  as  to  the  best  hours  of  school 
opening  and  closing ;  the  exact  number,  position  and  length  of  recita- 
tion and  recess  periods ;  whether  diversity  of  occupation,  gymnastics, 
etc.,  furnish  real  relief  and  to  what  extent;  amount  of  home  study 
desirable,  and  other  matters  of  less  importance.  These  questions 
will  scarcely  be  solved  by  investigating  fatigue  alone,  the  causal 
factors  being  more  diverse  and  complex  than  that  term  technically 
covers.  A  proper  line  of  efit'ort  for  the  practical  educator  is  not  to 
study  fatigue  less,  but  to  make  fewer  assumptions  as  to  its  presence 
and  amount,  and  to  study  just  as  conscientiously  the  other  causes 
of  temporary  mental  inability. 

After  thus  covering  the  accomplished  work  of  this  field,  it  re- 
mains to  decide  how  much  the  diurnal  course  of  efficiency  is  regularly 
affected  by  this  very  important  factor. 

Joteyko^  considers  fatigue  a  means  of  defence  of  the  organism, 
operating  in  three  ways:  (1)  it  produces  paralysis  of  the  nerve 
terminations  as  an  immediate,  physiological  defence;  (2)  the  traces 
left  by  the  unpleasant  sensations  tend  to  ward  off  similar  returns — 
are  a  preventive,  psychological  defence;  (3)  while  as  a  consecutive 
defence  it  renders  the  organism  more  resistant  to  fatigue.  The  last 
suggests  Binet's  assertion-  that  "even  a  book  could  be  written  en- 
titled 'Necessity  of  Fatigue  for  Physical  and  Mental  Hygiene'." 
In  any  event,  fatigue  lowers  the  expenditure  of  energy  by  intro- 
ducing more  inefficient  performance.  This  is  true  of  physiological, 
sensory  and  mental  functioning.  Its  approach  should,  therefore, 
herald  a  diminished  motor  force,  speed  and  control;  a  lessened  sen- 
sory discrimination;  and  a  reduced  mental  speed,  regularity  and 
accuracy.  This  being  granted,  the  first  and  perhaps  most  obvious 
thing  about  fatig-ue  in  relation  to  our  problem  is  that  it  does  not 
affect  all  our  functions  simultaneously  or  evenly,  yet  it  is  sometimes 
discussed  as  if  it  did.  This  may  partly  be  ascribed  to  its  confusion 
with  feelings  of  fatigue,  which  seem  to  us  subjectively  to  cause  a 

^ '  La  Fatigue  comme  Moyen  de  Defense  de  I'Organisme,'  C.R.,  IV.   Cong. 
Int.  de  Psych.,  Paris,  230-231.      1901. 
^  Binet  et  Henri,  op.  cit.,  p.  302. 


88  DIURNAL    COURSE    OF    EFFICIENCY 

general  and  pronounced  decline  of  all  our  capabilities.      But  the 
distinction  between  them  is  imperative  because  the  difference  is  real. 

IV,    Inertness  and  Nervousness 

The  distinction  between  fatigue  and  inertness,  referred  to  above, 
needs  here  to  be  recalled  and  emphasized.  It  may  be  thought  that 
the  introduction  of  this  term  in  a  technical  sense  is  a  needless  sub- 
division of  terminology.  But  inertness  is  as  distinct  from  fatigue 
proper  as  weariness  is;  neither  is  it  the  same  as  the  latter,  as  some 
German  writers  have  assumed.  It  differs  from  fatigue  in  that  there 
is  not  present,  nor  could  there  conceivably  be  under  the  given  condi- 
tions, any  cell  decomposition,  clogging,  poisoning  or  other  histological 
characteristic  of  the  purely  fatigued  cell.  It  differs  from  feelings 
of  fatigue  in  that  it  has  a  different  physiological  basis  and  can  not 
be  so  thoroughly  eliminated  by  introduction  of  interesting  or  'rein- 
forcing' stimulations  of  any  sort.  It  may  be,  and  apparently  often 
is,  accompanied  by  feelings  similar  to  those  of  fatigue,  though  less 
unpleasant.  As  already  intimated,  the  condition  as  a  whole  may  be 
likened  (not  histologically)  to  that  of  a  well-advanced  convalescent 
who  suffers  no  pain  or  disagreeable  affections,  but  is  simply  weak 
and  may  be  feeling  well.  Cowles^  calls  cases  of  early  morning, 
relative  inefficiency  'pathological  fatigue,'  but  their  occurrence  is 
much  too  common  and  apparently  normal  for  that  to  be  wholly  ac- 
ceptable. Wagner-  also  calls  them  the  same,  in  reference  to  skin- 
insensitivity,  but  the  writer  is  inclined  to  the  other  view,  save  as  to 
particular  cases.  Inertness  is  a  condition  of  not  being  wholly  waked 
up  and  warmed  up,  and  is  normal  after  sleep  or  inactivity.^ 

Inertness  may  be  considered  a  condition  of  under-stimulation ; 
obversely,  nervousness  is  a  condition  of  over-stimulation — a  sort  of 
excessive  'warming-up'.  However  caused — whether  by  mere  excita- 
tion, by  feelings  of  fatigue,  by  disease  or  otherwise — there  can  be 
no  doubt  that  nervousness  acts  concomitantly  with  fatigue  in  setting 
the  limit  to  efficiency  in  certain  kinds  of  mental  work.  Other  kinds, 
as  referred  to  in  discussing  the  authors,  seem  benefited  by  a  mild 
amount  of  it.  The  same  things  may  be  said  about  other  human 
employments,  some  being  favored  by  nervousness— especially  those 

^Neurasthenia,  and  its  Mental  Symptoms,  Boston,  1-104.      1891. 

^  Unterricht  u.  Ermildung,  Berlin,   1-134.      1898. 

^  The  repugnance  experienced  by  so  many  people,  to  reassumption  of  their 
week-day  toils,  on  Monday,  after  a  day  of  rest  (?)  is  due,  in  part  at  least,  to 
some  such  a  deadening  by  inactivity.  '  Blue  Monday '  instances  getting  into 
harness  again  after  a  '  let-down.'  The  true  psychology  of  stretching  and  of 
gaping  would  also  shed  light  here. 


CAUSAL    FACTORS   IN    DIURNAL   EFFICIENCY    CURVE 


89 


requiring  speed,  as  exemplified  by  the  factory  employees — and  some 
impaired,  as  noted  in  the  discussion  of  various  accuracy  tests. 

The  extent  to  which  the  inefficiency  of  the  later  part  of  the  day 
is  due  to  weariness  and  how  far  to  real  fatigue  and  nervousness  is  a 
hard  question  to  solve.  Objective  tests,  whether  of  the  'spurt'  or 
prolonged  type,  probably  give  a  better  idea  of  the  real  capacity  at 
any  period  than  do  our  subjective  feelings,  while  the  latter  seem 
more  indicative  of  what  we  are  likely  to  do  under  ordinary  condi- 
tions. Effort  was  made  to  get  some  data  on  this  matter  by  having 
different  people  draw  daily  curves  of  their  efficiency  as  estimated 
by  their  feelings,  but  only  a  few  records  were  secured.  In  Fig.  4 
are  shown  such  curves  for  five  of  the  subjects  used  in  the  author's 
experiments. 


^wM 


^JVL 


6      8/0/22        f         6        &       /O     /2 
Fig.  6.      Diurnal  Curves  of  the  Subjective  Feeling  of  Efficiency. 


These  curves  would  be  more  interesting  for  comparison  with  the 
actual  records  of  the  subjects  if  the  operation  of  comparison  were 
less  intricate.  The  purport  of  the  paper  thus  far  has  been  against 
indiscriminate  lumping  of  physical  or  mental  functions  in  order  to 
get  some  sort  of  curve  of  '  general  ability '.  The  tests  and  test  periods 
were  too  few,  in  most  cases,  to  make  it  possible  for  separate  curves 
to  be  reliably  drawn  for  rate,  accuracy,  strength,  etc.,  and  this  was 
not  attempted,  save  in  the  rough  way  indicated  by  the  following 


90  DIURNAL    COURSE    OP   EFFICIENCY 

general  statements.  Subject  II.  seems  actually  to  follow  his  curve 
the  closest,  and  III.  the  least  closely,  relatively,  to  the  greatest  number 
of  tests.  On  the  whole  about  60  per  cent,  of  the  actual  curves  might 
be  said  to  resemble  the  affective  ones  rather  closely.  Strength  seems 
most  inversely,  and  addition  most  directly,  correlated  with  the  feel- 
ings, though  the  number  of  common  tests  is  too  small  to  make  this 
very  reliable. 

The  afternoon  drop  in  all  these  curves  and  the  high  night  feeling 
of  ability,  shown  in  all  but  one,  appear  to  be  rather  characteristic  of 
students.  Five  professors  and  a  number  of  students  have  told  the 
author  that  this  is  a  true  expression  of  their  feelings.  Much  better- 
ment occurs  where  there  is  need  of  'buckling  down'  to  some  par- 
ticular task  in  the  afternoon,  but  to  what  degree  this  takes  place  or 
is  possible  is  a  question. 

This  matter  of  the  relations  between  what  one  can  do,  is  likely 
to  do  and  does  do  is  one  upon  which  a  large  quantity  of  curves,  like 
those  presented  above,  would  probably  shed  some  light.  In  addition 
to  the  'general  tendencies'  in  these  curves,  to  which  attention  has 
been  called,  it  is  seen  that  all  of  the  five  estimate  themselves  at  a  low 
figure  for  the  first  period.  This  is  strictly  in  accord  with  the  fact 
disclosed  by  their  actual  tests.  Here  feelings  of  fatigue  apparently 
are  present.  However,  the  morning  feeling,  after  introspective 
analysis,  is  connected  by  four  of  them— the  other  being  uncertain— 
rather  directly  with  some  physical  basis,  while  that  of  the  afternoon 
is  referred  to  one  more  distinctively  mental.  Though  the  distinc- 
tions here  are  vague,  these  few  cases  suggest  that  there  are  'feelings 
of  inertness'  just  as  there  are  'feelings  of  fatigue'.  Theoretical  psy- 
chological principles  also  lead  to  this  supposition,  if  it  is  true  that 
inertness  as  described  is  a  fact.  From  the  evidence  in  hand  the 
relative  importance  of  these  various  factors  can  not  be  satisfactorily 
judged. 

V.     Sex  and  Age. 

It  has  been  pointed  out  frequently  in  the  preceding  pages  that 
there  seems  to  be  in  adults  a  tendency  for  females  to  reach  an  earlier 
maximum  of  ability  than  males,  and  children  than  females.  The 
greater  influence  of  fatigue  and  weariness  with  both  women  and 
children  is  apparent,  and  the  recovery  after  meals  and  reactions 
seems  also  greater.^ 

*  Of  200  persons  replying  to  a  questionnaire  sent  out  by  Partridge  ( '  Second 
Breath,'  Fed.  Hem.,  4.  1896-1897),  06  reported  experiences  of  physical  'second 
breath  ' — recuperation  with  slight  or  no  rest,  after  exercise — of  whom  30  were 
females  and  36  males ;  102  reported  mental  '  second  breath,'  of  whom  89  were 
females  and   13  males. 


CAUSAL    FACTORS    IX    DIURXAL    EFFICIENCY    CURVE  91 

This  running  down  in  children,  as  far  as  it  is  a  fact,  is  not  due 
to  uninteresting  teachers  wholly,  nor  yet  to  hard  work,  but  is  rather 
independent  of  occupation,  if  the  following  is  a  correct  interpreta- 
tion of  results  obtained  by  Rivers  and  Kraepelin^  from  experiments 
on  the  effect  of  intervals  of  rest  upon  work  ability.  Beginning  at 
8  A.M.,  the  subject  was  required  to  spend  four  half-hour  periods  in 
adding,  each  such  period  being  followed  by  a  half-hour  period  of 
rest.  Of  the  three  daj'^s'  results  that  were  used,  all  show  increase  of 
ability  after  the  first  pause,  but  only  one  day  shows  this  after  the 
second  pause,  and  none  after  the  third.  The  inference  was  that  the 
first  rest  was  enough  to  effect  complete  recovery  from  the  fatigue 
of  the  preceding  addition;  the  second  was  only  partially  enough; 
and  the  third  was  quite  inadequate.  But,  if  there  was  entire  re- 
cuperation  after  the  first  half  hour's  work,  unless  a  naturally  de- 
teriorating disposition  intervened,  the  second  and  third  rests  should 
have  been  quite  as  effective  as  the  first.  The  same  thing  comes  out 
even  more  positively  in  a  second  series  of  experiments,  similar  in 
every  way  to  the  former  save  that  an  hour's  rest  followed  a  half 
hour's  work.  In  this  case  the  greatest  efficiency  was  again  mani- 
fested after  the  first  rest  and  thence  there  was  a  steady  decline, 
though  the  first  half  hour's  point  of  deficiency  w^as  not  again  reached. 
This  was  taken  to  mean  that  the  practise  effect  and  momentum  were 
lest  in  the  large  rest  intervals,  while  the  fatigue  effect  was  too  great 
to  be  overcome  after  the  second  addition,  just  as  in  the  other  series. 
It  is,  however,  very  improbable  that  the  fatigue  eff'ect  would  last  over 
an  interval  long  enough  to  destroy  the  practise  eff'ect.  What  prob- 
ably took  place  was  a  normal  decline  that  was  merely  hastened  by 
the  special  fatigue  of  the  tasks  imposed  and  by  a  growing  lack  of 
interest.  Children  lose  in  efficiency  much  more  readily  than  adults, 
but  also  recuperate  more  rapidly.  The  reason  lies  in  the  facts  that 
they  enter  into  what  natively  interests  them  with  more  fatiguing 
zeal  than  adults,  while,  on  the  other  hand,  they  are  more  prone  than 
adults  to  surrender  to  their  feelings  of  fatigue  w^here  their  interest 
is  not  so  intimately  engaged.  To  a  lesser  extent  the  same  is  true  of 
women. 

VI.     Brief  Summary. 

It  has  been  urged  that  the  night-day  rhythm  imposes  on  us  cor- 
responding periods  of  sleep  and  activity  whose  recurrence  is  the 
basic  condition  of  diurnal  periodicity  in  efficiency.  The  sleep  effect 
is  prolonged  beyond  waking  as  a  sort  of  inertness  which  is  neither 
real  fatigue  nor  merely  feelings  of  fatigue,  but  is  usually  accom- 

^ '  Ermiidung  u.  Erholung,'  Psych.  Arbeiten,  2:    627-678.      1896. 


92  DIURNAL    C0VF8E    OF    EFFICIENCY 

panied  by  feelings  of  inertness  or  of  fatigue,  or  both.  It  is  pro- 
nouncedly manifest  in  muscular  abilities,  especially  strength,  but 
seems  less  and  less  apparent  and  persistent  as  the  mental  field  is 
entered.  The  process  of  growing  awake  is  accelerated  by  a  progres- 
sive increase  of  sensorial  responsiveness  which  successive  stimuli, 
acting  cumulatively,  seem  to  entail  on  the  organism,  and  this  con* 
tinues  till  a  normal  limit  is  reached  or  some  modifying  factor  inter- 
feres. Chief  among  such  factors  are  personal  habits,  meals,  fatigue 
and  feelings  of  fatigue,  nervousness,  sex  and  age.  The  effects  of 
habits  (physical,  social,  mental,  etc.)  and  of  meals  vary  according 
to  the  particular  case,  but  generally  speaking  they  institute  a  recur- 
rence of  like  conditions,  effective  even  during  the  temporary  discon- 
tinuance of  the  habits.  Real  fatigue  sets  the  limit  to  the  absolute 
maximum  of  efficiency,  but  it  is  probable  that  feelings  of  fatigue 
have  more  to  do  with  the  curve  of  our  ordinary,  practical  efficiency 
— of  what  we  actually  accomplish.  It  appears  that  women  expend 
themselves  proportionately  more  energetically  than  men  in  things 
in  which  they  are  intimately  interested,  and  at  the  same  time  that 
their  feelings  of  fatigue  are  stronger  and  exercise  a  more  deterrent 
influence  w^here  their  personal  interests  are  not  so  immediately  con- 
cerned. This  seems  increasingly  true  of  children,  and  hence  we  find 
in  these  two  groups  a  corresponding  inclination  to  an  earlier  maxi- 
mum of  efficiency,  but  complicated  by  a  more  facile  recuperation. 


E.     CONCLUSION 

The  attitude  of  the  author  in  this  paper  has  been  conservatively 
favorable  to  the  idea  of  a  few,  broad  diurnal  variations  of  a  rather 
general  nature,  coexisting  with  more  numerous  and  intensive  varia- 
tions in  individuals.  Such,  in  fact,  seems  to  be  the  outcome  of  the 
investigation  and  of  the  collation  of  data  from  other  sources.  Scien- 
tifically, the  application  of  such  a  conclusion  is  both  direct  and  valu- 
able. For  its  truth  carries  with  it  the  suggestion  that  psychological 
and  physiological  investigators  would  be  obliged  to  take  into  con- 
sideration more  conscientiously  than  heretofore  the  fact  of  period- 
icity in  individuals.  Comparative  experiments  should  not  be  per- 
formed indifferently  at  varying  times  of  different  days,  if  exact 
results  are  to  be  expected.  Not  only  are  some  variations  of  ability, 
between  certain  periods,  as  great  or  greater  than  sex  differences  in  a 
homogeneous  group,  but  some  of  the  latter  may  possibly  be  accounted 
for  by  reference  to  the  differences  between  the  diurnal  cycles  of  the 
two  sexes. 

"When  it  comes  to  making  a  more  practical  application  of  the 
fact  of  periodic  variation,  w^e  become  principally  interested  in  the 
quantitative  value  of  the  differences.  If  only  a  slight  difference 
occurs  between  the  extremes  of  diurnal  efficiencies,  we  should  doubt- 
less take  no  account  of  it  in  any  voluntary  ordering  of  our  lives. 
Even  in  the  event  of  a  larger  difference,  our  peculiar  subjective 
organization  makes  it  a  question  worth  asking  by  each  person  whether 
the  reduction  of  the  inefficiency  at  any  period  should  be  attempted, 
since  such  incompetency  at  one  period  may  often  insure,  in  his  in- 
dividual case,  better  subsequent  work  than  otherwise  would  have 
been  performed.  Many  writers  are  on  record  as  being  unable  to  com- 
pose at  certain  times,  perhaps  for  days,  weeks  or  even  months.  The 
explanation  of  these  periods  of  enforced  inactivity  furnishes  a  good 
problem  for  investigation,  but  one  can  scarcely  disbelieve  that  they 
contribute,  in  some  way  and  degree,  to  the  betterment  of  future 
functioning.  There  is  here  a  practical  problem  for  every  one  to 
solve  in  his  own  case;  and  at  the  same  time  a  problem  of  general 
scientific  interest. 

A  general  expression  of  the  quantitative  differences  between  the 

efficiency  at  dift'erent  times  of  the  day  could  be  given,  if  records  for 

15  days— 10  periods  each— of  100  individuals,  were  available  in  a 

number  of  the  motor  and  mental  activities.     The  figures  of  the  wire- 

7  93 


94  DIURNAL    COURSE    OF   EFFICIENCY 

stitchers  (p.  35)  offer  material  for  illustration.  The  average  of  the 
maximal  and  minimal  number  of  magazines  handled  by  an  operative 
approximates  her  mean  speed  per  day.  Calculation  shows  the  sub- 
jects to  be,  at  the  minimal  period,  below  their  respective  averages, 
by  the  following  per  cents. :  5,  6,  4,  13,  7,  6,  7,  3.  This,  of  course,  is 
very  rough,  as  it  takes  no  account  of  the  reliabilities  of  the  various 
figures;  but  as  far  as  it  goes,  it  indicates  that  in  the  employment  of 
adults  in  manual  labor  one  might  expect  the  early  morning,  where 
the  minima  mostly  occur,  to  return  in  production  about  6  per  cent, 
less  than  the  day's  average,  and  from  10  to  12  per  cent,  less  than  at 
the  best  period.  Allowance  must,  however,  be  made  for  the  fact 
that,  if  the  women  had  worked  every  night,  instead  of  alternate  ones 
only,  these  results  would  doubtless  be  somewhat  altered. 

"Would  it  then  be  better  for  the  work-day  to  be  shortened  at  the 
morning  end  rather  than,  as  customarily,  at  the  night  end?  It 
might,  if  there  were  any  guarantee  that  the  employees  would  keep  to 
their  same  hours  of  rising;  otherwise  no  improvement  would  be  ex- 
pected. The  'warming  up'  must  be  effected,  whether  it  be  early  or 
not,  and  late  sleep  usually  retards  the  process.  Even  if  it  were 
practicable  for  an  employer  to  'exercise'  his  workers  vigorously  for 
an  hour  before  starting  them  on  pay-time  work  this  would  scarcely 
prove  profitable  to  him,  because  of  the  involved  expenditure  of 
energy  needed  in  their  actual  work ;  and  it  would  only  be  profitable 
in  case  of  a  shortened  day  and  time-work.  In  piece-work,  since  pay  is 
dependent  solely  upon  the  amount  done  and  not  upon  the  time  con- 
sumed, there  is  nothing  in  the  problem  of  diurnal  rhythms  that  would 
interest  the  employer,  save  when  the  rapidity  with  which  he  might 
want  a  special  job  finished  is  in  question.  Even  in  this  instance,  the 
application  would  be  limited  to  cases  in  which  extra  'hands'  were  to 
be  secured  for  the  occasion — that  is,  they  could  be  hired  only  for  their 
periods  of  high  efficiency;  this  would  hold  good  also  for  part-time 
time-workers — because  any  reassignment  of  his  'regulars'  to  such 
special  'rush'  work  would  be  governed  by  the  actual  amount  of  work 
required  to  get  out  on  time  the  regular  jobs  on  hand.  But  it 
would  be  of  interest  to  the  employee,  if  the  extra  exercise  could  be 
endured,  since  it  would  enable  him  to  start  in  at  a  rate  which  he 
must  else  more  slowly  attain.  Beyond  this,  there  seems  no  practical 
industrial  application  of  any  consequence. 

As  before  stated,  the  practical  value  of  investigations  of  this 
question  has  perhaps  most  particular  reference  to  school  life.  Most 
of  them  have  been  carried  on  with  this  in  view :  whole  curricula  have 
been  suggested,  ordered  in  accordance  with  the  results  of  different 
researches.      It  will  be  clear  to  the  reader  of  the  preceding  pages 


CONCLUSION  95 

that  such  curricula  rest  on  insecure  bases  as  yet,  but  that  the  em- 
pirical work  has  not,  therefore,  been  without  value.  The  main  result 
of  the  present  research,  in  this  connection,  consists  in  restablishing 
a  principle  already  well  known  in  the  pedagogical  field,  but  not  well 
enough  recognized.  Kraepelin's  thought  that  'the  present  arrange- 
ment of  school  programs  makes  it  a  necessity  to  have  tedious  teachers 
in  whose  classes  the  pupils  may  rest  themselves  by  inattention'  may 
have  some  truth  in  it,  but  it  is  much  more  worth  noting  that  the 
most  wholesome  and  economical  development  of  the  pupil  makes  it 
necessary  to  have  interesting  teachers  in  whose  classes  the  pupils 
may  rest  themselves  by  a  more  '  f rictionless, '  and  develop  themselves 
by  a  more  fully  utilized,  expenditure  of  energy.  The  feelings  of 
fatigue,  to  which  they  are  often  exposed,  are  more  deadening  intel- 
lectually than  the  real  fatigue  of  a  day's  interesting  work  and,  in 
addition,  do  not  represent  actually  growth f id  exercise  of  the  func- 
tions concerned. 

As  far  as  older  people  are  concerned,  this  principle  can  be  ap- 
plied somewhat  similarly.  The  feelings  of  languor  and  weariness, 
to  w^hich  one  may  become  more  subject  as  he  indulges  in  them,  might 
more  and  more  be  made  to  disappear,  as  far  as  they  are  not  due  to 
structural  defects  or  any  constant  and  uncontrollable  cause,  if  a 
definite  course  of  activity  were  consistently  pursued  in  spite  of  them. 
In  this  case,  a  sort  of  artificial  interest  ultimately  replaces  the  native 
spontaneity  of  the  children,  and  institutes  a  condition  of  less  ex- 
penditure of  energy  in  performing  the  given  act  at  the  given  time. 
Kraepelin  is  of  the  opinion  that  'every  human  being  has  his  own 
peculiar  way  of  work,  which  usually  shows  itself  regularly  in  the 
same  manner  during  every  working  period.'  That  is  too  sweeping, 
but  it  is  probable  that  the  older  one  grows  the  more  it  tends  to  be- 
come true,  because  habits  become  more  firmly  ingrained. 

Perhaps  a  few  remarks  should  be  made  as  to  the  existence  of  so- 
called  'morning  workers'  and  'night  workers.'  When  the  evidence 
of  the  preceding  pages  is  reviewed,  especially  that  concerning  stu- 
dents and  authors,  their  existence  can  scarcely  be  questioned.  The 
Germans  have  long  accepted  the  matter  as  settled  and  Kiilpe  can  be 
cited  as  a  splendid  example  of  the  fact  involved — as  a  night  worker. 
Here  again  the  quantitative  aspect — how  many  the  persons  and  how 
much  the  difference — are  the  all-important  practical  considerations, 
and  here  again  it  must  be  said  that  ample  data  for  their  determina- 
tion are  not  as  yet  at  hand. 

The  range  of  the  results  set  forth  in  this  paper  has  been  so  ex- 
tensive that  a  definite  impression  as  to  where  their  main  tendencies 
lie  may  still  be  lacking.     For  that  reason  a  method  was  diligently 


96  DIURNAL    COURSE    OF    EFFICIENCY 

sought  by  which  they  could  be  presented,  either  tabularly  or  graph- 
ically, in  such  a  way  as  to  indicate  this  in  small  scope.  However, 
when  one  attempts  properly  to  weight  data,  obtained  from  diurnal 
periods  varying  in  number  from  2  to  24 ;  from  various  measurements 
of  various  activities;  from  subjects  of  varying  number,  age  and  sex; 
and  under  other  varying  conditions— the  task  is  found  to  be  quite 
hopeless.  This  is  not  strange,  however,  considering  that  even  the 
'laws'  of  physics  can  not  always  be  expressed  in  one  figure  or 
formula.  For  instance,  expansion  of  volume  by  heat  has  several 
coefficients  for  solids;  a  constant  one  for  gases;  two  for  liquids, 
which  only  partly  hold  true;  while  water  in  certain  phases  exhibits 
phenomena  contrary  to  the  general  law.  Much  more  do  individuals 
differ  psj^chologically.  After  all,  if  all  the  figures  in  the  text  were 
reduced  to  some  percentage  basis,  they  would  still  be  incomparable 
for  this  reason,  that  an  increased  efficiency  of  10  per  cent,  in  one 
case  would  probably  not  at  all  mean  the  same  in  reality  as  an  in- 
crease of  10  per  cent,  in  another  function.  Such  a  summary  would 
be  satisfactory  in  its  compactness,  but  misleading  as  to  fact.  For 
the  chief  specific  conclusions,  therefore,  the  reader  is  referred  to 
the  brief  summaries  on  pages  13,  14,  40,  69,  91,  which  together  cover 
the  whole  investigation  on  its  empirical  side. 


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